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+% \iffalse meta-comment
+%
+%% File: groupthm.dtx
+%
+% Copyright (C) 2022 Maximilian Keßler
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% -----------------------------------------------------------------------
+%<package>\ProvidesExplPackage{groupthm}{2022/01/17}{0.0.1}{Grouped theorems.}
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\usepackage{mkessler-todo}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \pkg{groupthm} package^^A
+% }
+%
+% \author{^^A
+%      Maximilian Keßler
+% }
+%
+% \date{Released 2022-01-12}
+%
+% \maketitle
+%
+%
+% \NewDocumentCommand{\kw}{m}
+% {%
+%  \texttt{#1}%
+% }
+%
+% \NewDocumentCommand{\vocab}{m}
+% {%
+%  \emph{#1}%
+% }
+% 
+% \ExplSyntaxOn
+% \NewDocumentCommand { \mymeta } { O{} m }
+% {
+%   \meta[#1]{#2}
+%   \__codedoc_special_index_module:nnnnN { #2 } { #2 } { meta } { usage } { \c_false_bool}
+% }
+% \ExplSyntaxOff
+%
+%
+%
+% \begin{documentation}
+% 
+% \tableofcontents
+% \listoftodos
+% \newpage
+% 
+% \begin{itemize}
+%   \item Inheritance
+%   \item Appending to groups
+%   \item default group integration
+%   \item better error message to avoid low level tex errors in any case
+%   \item potentially: detection of star / nonstar misuse
+%   \item add command to define group rule for all existing groups
+%   \item various info commands on defined groups?
+%   \item debugging information?
+% \end{itemize}
+% A central thing in \LaTeX is the usage of \enquote{theorems}.
+% With \enquote{theorems} we actually mean \enquote{environments} that typically
+% have a title, some style applied to their contents and are numbered throughout 
+% the document, often later referenced by number and / or name.
+% 
+% Mechanisms for generating such environments are packages like
+% \pkg{amsthm}, \pkg{ntheorem}, \pkg{thmtools}.
+% 
+% While the mechanism in \pkg{thmtools} are pretty versatile and suffice
+% for almost all needs, it is pretty time-consuming to largely change
+% the behavior of environments, or have small variants of these.
+% 
+% This package aims at both providing a versatile mechanism, \mymeta{theorem group}s,
+% to structure theorems into groups that can subsequently easily altered,
+% as well as a mechanism for easily generating \mymeta{theorem families}.
+% 
+% As the author is of the opinion that of the mentioned theorem controlling packages
+% \pkg{thmtools} provides the most versatile interface, the \pkg{groupthm}
+% will be working on top of \pkg{thmtools} and use this as a backend for declaring
+% the \mymeta{theorem}s themselves.
+% 
+% Thus, any styles supported by \pkg{thmtools} will be supported by \pkg{groupthm}
+% as well, by passing them to \pkg{thmtools}.
+% 
+% \section{Concepts}
+% 
+% \subsection{Theorem groups}
+% \label{sec:theorem-groups}
+% A \mymeta{theorem group} is some named group holding some properties for
+% the \mymeta{theorem}s that are contained in this group.
+% Each \mymeta{theorem} can, when declared, be part of arbitrarily many \mymeta{theorem group}s,
+% and will be subject to the styles these groups defined.
+% 
+% This enables to group similar \mymeta{theorem}s and alter them at a late stage of
+% document development in a unique manner, by only having to change the
+% definition of the \mymeta{theorem group}, and not all \mymeta{theorem}s separately.
+% 
+% The properties. such a \mymeta{theorem group} can hold are as follows
+% 
+% 
+% \begin{description}
+%   \item[\kw{prefix}] A prefix (any \mymeta{token list}) that will be inserted
+%     before the theorem name of each member of this \mymeta{theorem group}.
+%   \item[\kw{suffix}] A suffix (any \mymeta{token list}) that will be
+%     inserted before the theorem name for each member of this \mymeta{theorem group}.
+%     This could be e.g.~some \enquote{$\star$} appended to the name to indicate
+%     variants of environments.
+%   \item[\kw{mapname}] A \mymeta{function} (some macro that takes exactly one argument)
+%     that is applied to the \kw{name}.
+%   \item[\kw{thmtools}] A \mymeta{clist} of key-value pairs that are passed to the underlying
+%     \pkg{thmtools} backend of the \mymeta{theorem}.
+%     This allows e.g.~to set the \kw{topskip} of a certain class of \mymeta{theorem}s.
+% \end{description}
+% 
+% The most versatile key here is certainly the \kw{thmtools} key,
+% providing the most customization to an end user (like you).
+% 
+% As mentioned, each \mymeta{theorem} can be member of arbitrary many \mymeta{theorem group}s,
+% and will posses their corresponding properties.
+% 
+% To adjust finer controlling of these \mymeta{theorem group}s, \mymeta{theorem group}s can inherit from each other, and \mymeta{theorem group}s are subject to a hierarchy that controls precedence in case
+% of conflicting properties of different \mymeta{theorem group}s a \mymeta{theorem} may be part of.
+% 
+% This hierarchy can of course be controlled by the user.
+% 
+% \subsection{Grouped theorems}
+% 
+% A \mymeta{grouped theorem} is just a theorem that is a member of
+% a given set of groups (possibly empty).
+% It behaves just a regular theorem, except that by changing the definition of
+% its theorem groups, we can alter its behavior.
+% 
+% 
+% It is the core concept of the \pkg{groupthm} package.
+% For brevity, we will often talk about \enquote{theorems},
+% although in fact we mean \enquote{grouped theorems}.
+% 
+% \subsection{Theorem families}
+% Often, one needs some small \mymeta{theorem variant}s of some \mymeta{theorem}, the most typical
+% example being \vocab{starred} version of \mymeta{theorem}s that are not numbered
+% in contrast to their counterparts.
+% 
+% \begin{verbatim}
+%   \begin{theorem}
+%     This theorem is numbered.
+%   \end{theorem}
+% 
+%   \begin{theorem*}
+%     This theorem is not numbered.
+%     Probably because we do not want a reference to it.
+%   \end{theorem*}
+% \end{verbatim}
+% \todo{insert code example output}
+% 
+% \pkg{groupthm} extends this idea and provides a versatile mechanism to define a
+% \mymeta{theorem family}, which is based on some \mymeta{theorem name} and
+% parses additional arguments / syntax to control the \mymeta{theorem groups}
+% that this environment is a part of.
+% 
+% So, in addition the name of a \mymeta{theorem}, the corresponding environment will
+% accept some options and toggle the membership of certain \mymeta{theorem groups},
+% thus further customizing its appearance.
+% 
+% This can lead e.g.~to usages like the following:
+% 
+% \begin{verbatim}
+%   \begin{theorem}*
+%     This theorem has a visual * at its name.
+%   \end{theorem}
+% \end{verbatim}
+% \todo{code}
+% 
+% Providing this consists of two parts:
+% declaring the \mymeta{theorem family} by listing the groups that can be toggled
+% by this \mymeta{theorem family}, and declaring the actual option parsing
+% of the \mymeta{theorem family}, which then controls the membership in these groups
+% (and of course prior to this the definition of the desired \mymeta{theorem group}s).
+% 
+% 
+% 
+% \subsection{General notions}
+% 
+% In many cases, there are a number of variants of some command,
+% call it for example \cs{Foo}.
+% Then the documentation will look like
+% %
+% \begin{function}{\NewFoo, \RenewFoo, \ProvideFoo, \DeclareFoo}
+%   Defines some \kw{foo} \ldots
+% \end{function}
+% %
+% and will not mention anything about the variants.
+% This follows some general naming convention that also \pkg{xparse} uses,
+% and is the following:
+% 
+%   \begin{description}
+%     \item[\cs{NewFoo}]
+% 
+%       Defines \kw{foo} if not defined already.
+%       This emits an error in case it has been defined yet.
+% 
+%     \item[\cs{RenewFoo}]
+% 
+%       Redefines \kw{foo} if defined already.
+%       This emits an error in case it has \emph{not} been defined yet.
+% 
+%     \item[\cs{ProvideFoo}]
+% 
+%       Defines \kw{foo} if it is not defined already.
+%       This does not emit an error if \kw{foo} is already defined
+%       (and has no effect in this case).
+% 
+%     \item[\cs{DeclareFoo}]
+% 
+%       Defines \kw{foo} in disregard of any
+%       existing definitions. Any old definition will be overwritten (if present).
+%   \end{description}
+% %
+%   The documentation margin will list all variants that are available,
+%   they follow their respective conventions.
+% 
+% 
+%   \begin{texnote}
+%     The \pkg{thmtools} package, unfortunately, dose not follow this convention,
+%     as its \cs{declaretheorem} command actually behaves like a \cs{newtheorem}.
+%     The reason for this is that \pkg{amsthm} already defines \cs{newtheorem}.
+% 
+%     Thus, actually, calls to \cs{NewGroupedTheorem} will have an underlying
+%     \cs{declaretheorem}, but you do not have to bother with this.
+%   \end{texnote}
+% 
+% \section{Theorem groups}
+% 
+% \subsection{Defining theorem groups}
+% 
+% \begin{function}{\NewTheoremGroup, \RenewTheoremGroup, \ProvideTheoremGroup, \DeclareTheoremGroup}
+%   \begin{syntax}
+%     \cs{NewTheoremGroup}\oarg{keys}\marg{theorem group}
+%   \end{syntax}
+%   
+%   This introduces a new \mymeta{theorem group} with the given name.
+%   The \mymeta{keys} available are the same as introduced in \autoref{sec:theorem-groups}:
+% 
+%   \begin{description}
+%     \item
+% 
+%       \kw{prefix} = \mymeta{token list}.
+%       Insert the \mymeta{token list} in front of the theorem name.
+% 
+%     \item
+% 
+%       \kw{suffix} = \mymeta{token list}.
+%       Insert the \mymeta{token list} after the theorem name.
+% 
+%     \item
+% 
+%       \kw{mapname} = \mymeta{function}.
+%       Apply this \mymeta{function} to the theorem name.
+% 
+%     \item
+% 
+%       \kw{thmtools} = $\{$\mymeta{clist}$\}$.
+%       Pass these options to \pkg{thmtools}.
+% 
+%   \end{description}
+% 
+%   For uniqueness of the given options, the \mymeta{clist} given to the \kw{thmtools} key
+%   has to be surrounded by a pair of braces.
+% 
+%   \begin{texnote}
+%     The \kw{mapname} is expected to be a function of \cs{fun:n}.
+%     It is subject to an \kw{x}-type expansion prior to being passed further to \pkg{thmtools}.
+%   \end{texnote}
+% 
+% \end{function}
+% 
+% \subsection{Controlling theorem group precedence}
+% 
+% \begin{function}{\DeclareTheoremGroupRule}
+%     \begin{syntax}
+% \cs{DeclareTheoremGroupRule}\oarg{keyname}%
+% \marg{theorem group 1}\marg{relation}\marg{theorem group 2}
+%     \end{syntax}
+%   
+%   This declares some relation between the two theorem groups,
+%   controlling their order of application in case a theorem is member
+%   of both groups.
+% 
+%   The \mymeta{keyname} can be one of \kw{prefix}, \kw{suffix}, \kw{mapname}, \kw{thmtools}.
+%   If present, it declares the corresponding relation only for this subkey.
+%   This can lead to \mymeta{theorem group 1} overwriting \mymeta{theorem group 2} when given
+%   contradictory \pkg{thmtools} options, but the \kw{prefix} of \mymeta{theorem group 1}
+%   being applied after the one of \mymeta{theorem group 2}.
+%   When the \mymeta{keyname} is not given, this applies to all keywords.
+% 
+%   \begin{texnote}
+%     The \mymeta{keyname} is just passed to the corresponding argument
+%     of the \kw{lthooks} package.
+%     If the option argument is not present, \kw{??} is used, this has the described effect.
+%   \end{texnote}
+% 
+%   The behavior of the relations is based on the \cs{DeclareHookRule} command
+%   from the \pkg{xparse} package, and all respective keys are in fact available,
+%   but typically not needed, so the reader of this manual is referred to the
+%   \todoref{lthooks} packages documentation for a list of the full keys.
+%   For us, the following list will suffice:
+% 
+%   \begin{description}
+%     \item[\kw{higher} or \kw{after} or \kw{\string>}]
+%       
+%       \mymeta{theorem group 1} takes precedence over \mymeta{theorem group 2}.
+%       Its \kw{prefix} is applied after the one of \mymeta{theorem group 2}.
+% 
+%     \item[\kw{lower} or \kw{before} or \kw{\string<}]
+% 
+%       \mymeta{theorem group 2} takes precedence over \mymeta{theorem group 1}.
+%       Its \kw{prefix} is applied after the one of \mymeta{theorem group 1}.
+% 
+%   \end{description}
+% 
+%   \begin{texnote}
+%     The \mymeta{relation} is first stripped,
+%     then checked if it matches either \kw{higher} or \kw{lower}
+%     and in this case replaced by the corresponding \pkg{lthooks} variant
+%     of the relation.
+%     The rest is passed as is to \pkg{lthooks} and thus subject to the usual
+%     normalization process of \pkg{lthooks}.
+%   \end{texnote}
+% 
+% \end{function}
+% 
+% 
+% \subsection{Inheritance of theorem groups}
+% \begin{function}{\AddTheoremGroupParent}
+%   \begin{syntax}
+%     \cs{AddTheoremGroupParent}\marg{theorem group 1}\marg{theorem group 2}
+%   \end{syntax}
+%   Declares \mymeta{theorem group 1} to \enquote{inherit} all properties
+%   of \mymeta{theorem group 2}.
+%   In other words, \mymeta{theorem group 2} is a parent of \mymeta{theorem group 1}
+%   in a usual inheritance graph.
+% 
+%   The definitions of the groups themselves are unchanged,
+%   but each new theorem defined with \mymeta{theorem group 1} will also
+%   have the properties of \mymeta{theorem group 2}.
+% 
+%   Inheritance is transitive, when defining a new theorem, we just flatten out the
+%   inheritance graph and apply all properties.
+% 
+%   Inheritance is subject to the usual theorem group hierarchies as discussed in \todoref.
+%   This can even yield to situations, where \mymeta{theorem group 1} inherits
+%   from \mymeta{theorem group 2}, but \mymeta{theorem group 2} overwrites
+%   \mymeta{theorem group 1}.
+% \end{function}
+% 
+% \subsection{Appending to theorem groups}
+% \begin{function}{\AppendToTheoremGroup}
+%   \begin{syntax}
+%     \cs{AppendToTheoremGroup}\oarg{keys}\marg{theorem group}
+%   \end{syntax}
+%   Adds the properties given as \mymeta{keys} to the theorem group.
+%   The syntax for the \mymeta{keys} is the same as in \cs{NewTheoremGroup}.
+% \end{function}
+% 
+% \subsection{Default theorem groups}
+% 
+% There are a number of theorem groups that \pkg{groupthm} will initially declare
+% and that have certain special treatment in some places.
+% 
+% \begin{function}{all}
+%   Every declared grouped theorem is a member of this group.
+% 
+%   Initially, this group has no effect (i.e.~an empty property list).
+%   It can be redefined by the user to alter the behavior of all grouped theorems
+%   in a unified way.
+% 
+%   It is the lowest theorem group in the hierarchy by default.
+% \end{function}
+% 
+% \begin{function}{starred}
+%   This is group that shall represent the standard variant of theorems that
+%   are called with a \enquote{*} in the environment name.
+%   Theorems of this group are not numbered.
+% 
+%   The user should not add theorems to this group by hand,
+%   as this is handled in a unified way by default.
+%   \todoref{}
+% 
+%   It is the highest theorem group in the hierarchy by default,
+%   except for \texttt{unnumbered},
+%    with which it has no relation.
+% \end{function}
+% \addtocounter{footnote}{-1}
+% 
+% \begin{function}{unnumbered}
+%   Theorems in this group are not numbered.
+% 
+%  It is the highest theorem group in the hierarchy by default,
+%  except for \cs{starred},
+%  with which it has no relation.
+% \end{function}
+% 
+% The reason for the two groups \kw{starred} and \kw{unnumbered}
+% to both exist is that the \kw{starred} group is \emph{meant} to be applied
+% to theorems that were called with a \enquote{*} in their name (thus the name),
+% whereas the \enquote{unnumbered} group \emph{means} that the environment
+% is 'just unnumbered'.
+% 
+% This has two reasons:
+% First, this enables more fine-tuning of the behavior of the theorems in post-processing
+% of a document.
+% Second, more importantly, this distinguishes semantically between the environments
+% \kw{theorem} and \kw{theorem*}, even if \kw{theorem} is in the \kw{unnumbered} group.
+% 
+% So assuming that \kw{theorem} is member of the \kw{unnumbered} group, both calls
+% 
+% \begin{verbatim}
+%   \begin{theorem}
+%     This is not numbered.
+%   \end{theorem}
+%   \begin{theorem*}
+%     This is not numbered.
+%   \end{theorem*}
+% \end{verbatim}
+% 
+% are defined and will produce the same result by default, but we could still
+% change the definition of the \kw{starred} group later to do anything we want.
+% 
+% \begin{texnote}
+%   The mentioned hierarchies are kept intact for newly defined theorem groups,
+% i.e.~for each new such group, two theorem group rules are created.
+% \end{texnote}
+% 
+% \section{Grouped Theorems}
+% 
+% \subsection{Defining grouped theorems}
+% 
+% \begin{function}{\NewGroupedTheorem, \ProvideGroupedTheorem}
+%   \begin{syntax}
+%     \cs{NewGroupedTheorem}\oarg{keys}\marg{theorem name}
+%   \end{syntax}
+%   This defines \mymeta{theorem name}  as a new theorem environment.
+%   Its properties can be set by the following keys:
+% 
+%   \begin{description}
+% 
+%     \item
+% 
+%       \kw{name} $=$ \mymeta{displayed name}.
+%       If given, this is the displayed name of the environment in the document.
+%       If not present, the \mymeta{theorem name} is also used as the \mymeta{displayed name}
+%       in capitalized form.
+% 
+%     \item
+% 
+%       \kw{group} $=$ \marg{clist}
+% 
+%       Makes this theorem a member of the listed groups.
+%       It will inherit all respective properties of these groups.
+% 
+%       If groups are present more than one time, this has no (additional) effect.
+% 
+%     \item
+% 
+%       \kw{thmtools} = \marg{clist}
+% 
+%       Passes these option to the \pkg{thmtools} environment that is declared internally.
+%     
+%   \end{description}
+% \end{function}
+% 
+% \begin{function}{\NewGroupedTheorem*,\ProvideGroupedTheorem*}
+%   \begin{syntax}
+%     \cs{NewGroupedTheorem*}\oarg{keys}\marg{theorem name}
+%   \end{syntax}
+%   Behaves the same as \cs{NewGroupedTheorem},
+%   but also adds the theorem to the default \kw{unnumbered} group,
+%   thus resulting in the environment not being numbered.
+% 
+%   This is thus equivalent to using \cs{NewGroupedTheorem} and adding the
+%   \kw{unnumbered} group.
+% \end{function}
+% 
+% \begin{function}{\NewTheorem, \ProvideTheorem}
+%   \begin{syntax}
+%     \cs{NewTheorem}\oarg{keys}\marg{theorem name}
+%   \end{syntax}
+% 
+%   This behaves essentially the same as \cs{NewGroupedTheorem},
+%   but will define two grouped theorems, namely \mymeta{theorem name} and \mymeta{theorem name*}.
+% 
+%   The \mymeta{theorem name*} environment has the same properties as the \mymeta{theorem name},
+%   but will be member of the \kw{starred} theorem group.
+%   It is thus not recommended to call \cs{NewTheorem}
+%   with an actual \enquote{*} in the environment name, since both environments
+%   will be generated.
+% \end{function}
+% 
+% \begin{function}{\NewTheorem*, \ProvideTheorem*}
+%   \begin{syntax}
+%     \cs{NewTheorem}\oarg{keys}\marg{theorem name}
+%   \end{syntax}
+%   Combines the behavior of \cs{NewGroupedTheorem*} and \cs{NewTheorem}, thus
+%   declaring \mymeta{theorem} to (additionally) be member of the \kw{unnumbered}
+%   and \mymeta{theorem*} to (additionally) be member of the \kw{starred} group.
+% 
+%   As mentioned in \todoref, by default both environments will behave the same.
+% \end{function}
+% 
+% \subsection{Defining families of grouped theorems}
+% 
+% \begin{function}{\NewGroupedTheoremFamily, \ProvideGroupedTheoremFamily}
+%   \begin{syntax}
+%     \cs{NewTheoremFamily}\oarg{keys}\marg{theorem name}
+%   \end{syntax}
+% 
+%   Defines a family of grouped theorems.
+%   The \mymeta{keys} accept the same arguments as the \cs{NewGroupedTheorem} macro.
+%   However, for each \emph{subset} of the given groups,
+%   a grouped theorem is defined.
+% 
+%   These grouped theorems are not meant to be accessed directly (but could),
+%   so we omit their actual (internal) names here.
+%   To call these, some \kw{GroupedTheoremFamilyOptions} have to specified,
+%   see \cs{NewGroupedTheoremFamilyOptions}.
+% \end{function}
+% 
+% \begin{function}{\NewGroupedTheoremFamily*, \ProvideGroupedTheoremFamily*}
+%   Behaves the same as \cs{NewGroupedTheoremFamily}, but also adds each variant
+%   to the default \kw{unnumbered} group, thus resulting in the environments not being
+%   numbered.
+% 
+%   This is \emph{almost} equivalent to calling \cs{NewGroupedTheoremFamily}
+%   with the \kw{unnumbered} group being present, as it does not generate the variants
+%   where the \kw{unnumbered} group is not present.
+% \end{function}
+% 
+% \begin{function}{\NewTheoremFamily, \ProvideTheoremFamily}
+%   This behaves essentially the same as \cs{NewGroupedTheoremFamily},
+%   but will add the \kw{starred} group to the list of groups and also generate variants
+%   for these.
+% 
+%   It is thus not recommended to call \cs{NewTheoremFamily} with the \kw{starred}
+%   group explicitly given, since this is added anyways.
+% \end{function}
+% 
+% \begin{function}{\NewTheoremFamily*, \ProvideTheoremFamily*}
+%   Combines the behavior of \cs{NewGroupedTheoremFamily*} and \cs{NewTheoremFamily}, thus
+%   declaring all variants to (additionally) be member of the \kw{unnumbered}
+%   group, and also generates definitions with and without the \kw{starred} group.
+% 
+%   As mentioned in \todoref, by default both environments will behave the same.
+% \end{function}
+% 
+% 
+% \begin{function}{\AddTheoremToGroup}
+%   \begin{syntax}
+%     \cs{AddTheoremToGroup}\marg{theorem group}
+%   \end{syntax}
+%   
+%   Means that the current invocation of a theorem family should
+%   call the theorem variant with the given group.
+% 
+%   Can only be used in the body of \cs{NewGroupedTheoremFamilyOptions} or similarly.
+% \end{function}
+% 
+% \begin{function}
+% {
+%   \NewGroupedTheoremFamilyOptions, \RenewGroupedTheoremFamilyOptions,
+%   \ProvideGroupedTheoremFamilyOptions, \DeclareGroupedTheoremFamilyOptions
+% }
+% \begin{syntax}
+%   \cs{NewGroupedTheoremFamilyOptions}\marg{theorem name}\marg{argument specifiation}%
+%   \marg{selection body}
+% \end{syntax}
+% 
+% Defines a new environment with options, given by \mymeta{theorem name}.
+% The \mymeta{argument specification} can be any valid \pkg{xparse} argument specification.
+% 
+% The \mymeta{selection body} is there to process the options of
+% the \mymeta{argument specification} and select which variant of the \mymeta{theorem name}
+% to enter.
+% The arguments are available as usual with \pkg{xparse} by \kw{\#1}, \kw{\#2}, \ldots
+% 
+% The body may also call any number of \cs{AddTheoremToGroup} calls,
+% which enables the corresponding groups.
+% 
+% When the environment is called within the document, the options are parsed
+% as with \pkg{xparse} and the \mymeta{selection body} is executed.
+% Immediately after, the theorem variant of \mymeta{theorem name} with the specified groups
+% by \cs{AddTheoremToGroup} is called.
+% 
+% At the end of the environment, the \mymeta{selection body} is executed again and the
+% called theorem variant is ended again.
+% 
+% The possible theorem variants that the newly declared environment will call
+% \emph{have to be generated subsequently} by a call to the \cs{NewGroupedTheoremFamily}
+% function.
+%   
+% \end{function}
+% 
+% \begin{function}
+%   {
+%     \NewGroupedTheoremFamilyOptions*, \RenewGroupedTheoremFamilyOptions*,
+%     \ProvideGroupedTheoremFamilyOptions*, \DeclareGroupedTheoremFamilyOptions*
+%   }
+%   \begin{syntax}
+%   \cs{NewGroupedTheoremFamilyOptions*}\marg{theorem name}\marg{argument specifiation}%
+%   \marg{selection body}
+%   \end{syntax}
+%   
+%   Does the same as \cs{NewGroupedTheoremFamilyOptions},
+%   but calls the variants with the additional \kw{unnumbered} group.
+% 
+%   The possible theorem variants have to be generated
+%   with the \cs{NewGroupedTheoremFamily*} command before.
+% 
+% \end{function}
+% 
+% \begin{function}
+%   {
+%     \NewTheoremFamilyOptions, \RenewTheoremFamilyOptions,
+%     \ProvideTheoremFamilyOptions, \DeclareTheoremFamilyOptions
+%   }
+%   \begin{syntax}
+%     \cs{NewTheoremFamilyOptions}\marg{theorem name}\marg{argument specifiation}%
+%     \marg{selection body}
+%   \end{syntax}
+% 
+%   This behaves essentially the same as \cs{NewGroupedTheoremFamilyOptions},
+%   but also declares the environment \mymeta{theorem name*},
+%   which behaves the same but calls the theorem variants with the additional \kw{starred}
+%   subgroup.
+% 
+%   The possible theorem variants have to be generated with the \cs{NewTheoremFamily}
+%   command before.
+%   
+% \end{function}
+% 
+% \begin{function}
+%   {
+%     \NewTheoremFamilyOptions*, \RenewTheoremFamilyOptions*,
+%     \ProvideTheoremFamilyOptions*, \DeclareTheoremFamilyOptions*
+%   }
+%   \begin{syntax}
+%     \cs{NewTheoremFamilyOptions*}\marg{theorem name}\marg{argument specifiation}%
+%     \marg{selection body}
+%   \end{syntax}
+% 
+%   Combines the behavior of \cs{NewGroupedTheoremFamilyOptions*} and \cs{NewTheoremFamilyOptions},
+%   thus declaring both \mymeta{theorem name} and \mymeta{theorem name*} environments,
+%   the latter calling the \kw{starred} variants of the theorem family,
+%   and both of them calling \kw{unnumbered} variants of the family.
+% 
+%   The possible theorem variants have to be generated with the \cs{NewTheoremFamily*}
+%   command before.
+% 
+% \end{function}
+% 
+% \section{\LaTeX3 interface}
+%
+% There is also an underlying \LaTeX3 interface provided by the package
+% (and in fact, all prior documented macros are just wrappers around this
+% internal programming interface.
+%
+% When building on top of this package, you can also use this interface,
+% which is possibly easier to use.
+%
+% In general, for functions that use key-value syntax, there are typically
+% three (public) versions of the command, namely
+%
+% \begin{itemize}
+%   \item A \LaTeX3 command that requires all key-values as mandatory arguments,
+%     so this does not use the key-value interface.
+%     Use this if you already know with which keys you deal and know their
+%     corresponding values.
+%   \item A \LaTeX3 command having the first argument accepting the keys as a
+%     comma-separated list.
+%     Use this if you want to profit of the key-value syntax.
+%   \item A \LaTeX2e document command. These were documented before,
+%     and these just wrap the second type of command.
+% \end{itemize}
+% If the corresponding command would be something like \enquote{new foo},
+% The syntax will typically be
+% \begin{itemize}
+%   \item \cs{groupthm_new_foo:mmm}\mymeta{mandatory args}\mymeta{optional args},
+%     where the \mymeta{mandatory args} list the mandatory args of the \LaTeX2e
+%     interface, and the \mymeta{optional args} list the optional args
+%     of the key-value interface, but requiring them mandatory as well.
+%   \item \cs{groupthm_new_foo_from_keys:mmm}\marg{keys}\mymeta{mandatory args}
+%     where we pass a \texttt{clist} as the first argument and all mandatory args
+%     as further mandatory arguments.
+%   \item \cs{NewFoo}\oarg{keys}\mymeta{mandatory args},
+%     where the keys can be passed optionally.
+% \end{itemize}
+% 
+% \subsection{Theorem groups}
+%
+%
+% \begin{function}
+% {
+%   \groupthm_new_theorem_group_from_keys:nn,
+%   \groupthm_renew_theorem_group_from_keys:nn,
+%   \groupthm_provide_theorem_group_from_keys:nn,
+%   \groupthm_declare_theorem_group_from_keys:nn
+% }
+%   \begin{syntax}
+%     \cs{groupthm_new_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%   \end{syntax}
+%
+%    \LaTeX3 versions of \cs{NewTheoremGroup}, \cs{RenewTheoremGroup},
+%    \cs{ProvideTheoremGroup} and \cs{DeclareTheoremGroup}
+%
+% \end{function}
+% 
+%
+%
+% \begin{function}
+% {
+%   \groupthm_new_theorem_group:nnnnn,
+%   \groupthm_renew_theorem_group:nnnnn,
+%   \groupthm_provide_theorem_group:nnnnn,
+%   \groupthm_declare_theorem_group:nnnnn,
+%   \groupthm_new_theorem_group:nVVVV,
+%   \groupthm_renew_theorem_group:nVVVV,
+%   \groupthm_provide_theorem_group:nVVVV,
+%   \groupthm_declare_theorem_group:nVVVV
+% }
+%   \begin{syntax}
+%     \cs{groupthm_new_theorem_group:nnnnn}\marg{theorem group}\marg{prefix tl}
+%     \marg{suffix tl}\marg{mapname clist}\marg{thmtools clist}
+%   \end{syntax}
+%  
+% Non-keyval versions of
+% \cs{groupthm_new_theorem_group_from_keys:nn},
+% \cs{groupthm_renew_theorem_group_from_keys:nn},
+% \cs{groupthm_provide_theorem_group_from_keys:nn}
+% and
+% \cs{groupthm_declare_theorem_group_from_keys:nn}
+%
+% These take the individual values of the keyval keys directly, in the order
+% indicated by the syntax specification.
+% 
+% \end{function}
+% 
+%
+% \begin{function}{\groupthm_declare_theorem_group_rule:nnnn}
+%    \begin{syntax}
+%       \cs{groupthm_declare_theorem_group_rule:nnnn}\marg{keyname}\marg{theorem group 1}
+%       \marg{relation}\marg{theorem group 2}
+%    \end{syntax}
+%
+%  \LaTeX3 version of \cs{DeclareTheoremGroupRule}
+%
+% \end{function}
+%
+% 
+% \subsection{Grouped theorems}
+%
+% \begin{function}{\groupthm_new_grouped_theorem_from_keys:nn, \groupthm_provide_grouped_theorem_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_from_keys:nn}\marg{keys}\marg{environment name}
+%    \end{syntax}
+%   
+%   \LaTeX3 version of \cs{NewGroupedTheorem}, \cs{ProvideGroupedTheorem}
+% 
+%
+% \end{function}
+%
+% \begin{function}
+% {
+%   \groupthm_new_grouped_theorem_star_from_keys:nn,
+%   \groupthm_provide_grouped_theorem_star_from_keys:nn
+% }
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem_star_from_keys:nn}\marg{keys}\marg{environment name}
+%    \end{syntax}
+%
+% 
+%   \LaTeX3 version of \cs{NewGroupedTheorem*}, \cs{ProvideGroupedTheorem*}
+%
+%
+% \end{function}
+%
+%
+%
+% \begin{function}{\groupthm_new_theorem_from_keys:nn, \groupthm_provide_theorem_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_from_keys:nn}\marg{keys}\marg{environment name}
+%    \end{syntax}
+%   
+%   \LaTeX3 version of \cs{NewTheorem}, \cs{ProvideTheorem}
+% 
+%
+% \end{function}
+%
+% \begin{function}{\groupthm_new_theorem_star_from_keys:nn, \groupthm_provide_theorem_star_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_star_from_keys:nn}\marg{keys}\marg{environment name}
+%    \end{syntax}
+%
+%   \LaTeX3 version of \cs{NewTheorem*}, \cs{ProvideTheorem*}
+%
+% \end{function}
+%
+% 
+% \begin{function}
+% {
+%   \groupthm_new_grouped_theorem:nnnn,
+%   \groupthm_provide_grouped_theorem:nnnn,
+%   \groupthm_new_grouped_theorem_star:nnnn,
+%   \groupthm_provide_grouped_theorem_star:nnnn,
+%   \groupthm_new_theorem:nnnn,
+%   \groupthm_provide_theorem:nnnn,
+%   \groupthm_new_theorem_star:nnnn,
+%   \groupthm_provide_theorem_star:nnnn
+% }
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem:nnnn}\marg{environment name}\marg{groups clist}
+%       \marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+% 
+%   Non-keyval versions of above macros.
+%
+% \end{function}
+% 
+% 
+% \subsection{Theorem families}
+% 
+%
+% \begin{function}
+%   {
+%     \groupthm_new_grouped_theorem_family_from_keys:nn,
+%     \groupthm_provide_grouped_theorem_family_from_keys:nn
+%   }
+%   \begin{syntax}
+%     \cs{groupthm_new_grouped_theorem_family_from_keys:nn}\marg{keys}\marg{theorem family}
+%   \end{syntax}
+%
+%   The \LaTeX3 versions of \cs{NewGroupedTheoremFamily} and \cs{ProvideGroupedTheoremFamily}
+%
+% \end{function}
+% 
+% 
+% 
+% \begin{function}
+%   {
+%     \groupthm_new_grouped_theorem_family_star_from_keys:nn,
+%     \groupthm_provide_grouped_theorem_family_star_from_keys:nn
+%   }
+%   \begin{syntax}
+%     \cs{groupthm_new_grouped_theorem_family_star_from_keys:nn}\marg{keys}\marg{theorem family}
+%   \end{syntax}
+%
+%   The \LaTeX3 versions of \cs{NewGroupedTheoremFamily*} and \cs{ProvideGroupedTheoremFamily*}
+%
+% \end{function}
+% 
+% 
+%
+% \begin{function}
+%   {
+%     \groupthm_new_theorem_family_from_keys:nn,
+%     \groupthm_provide_theorem_family_from_keys:nn
+%   }
+%   \begin{syntax}
+%     \cs{groupthm_new_theorem_family_from_keys:nn}\marg{keys}\marg{theorem family}
+%   \end{syntax}
+%
+%   The \LaTeX3 versions of \cs{NewTheoremFamily} and \cs{ProvideTheoremFamily}
+%
+% \end{function}
+% 
+% 
+% 
+% \begin{function}
+%   {
+%     \groupthm_new_theorem_family_star_from_keys:nn,
+%     \groupthm_provide_theorem_family_star_from_keys:nn
+%   }
+%   \begin{syntax}
+%     \cs{groupthm_new_theorem_family_star_from_keys:nn}\marg{keys}\marg{theorem family}
+%   \end{syntax}
+%
+%   The \LaTeX3 versions of \cs{NewTheoremFamily*} and \cs{ProvideTheoremFamily*}
+%
+% \end{function}
+% 
+%
+% \begin{function}
+% {
+%   \groupthm_new_grouped_theorem_family:nnnn,
+%   \groupthm_provide_grouped_theorem_family:nnnn,
+%   \groupthm_new_grouped_theorem_family_star:nnnn,
+%   \groupthm_provide_grouped_theorem_family_star:nnnn,
+%   \groupthm_new_theorem_family:nnnn,
+%   \groupthm_provide_theorem_family:nnnn,
+%   \groupthm_new_theorem_family_star:nnnn,
+%   \groupthm_provide_theorem_family_star:nnnn
+% }
+%   \begin{syntax}
+%     \cs{groupthm_new_grouped_theorem_family:nnnn}\marg{theorem family}     
+%     \marg{groups}\marg{name}\marg{thmtools clist}
+%   \end{syntax}
+%
+%  The non-key-value versions of the prior macros.
+%
+% \end{function}
+% 
+% \end{documentation}
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% 
+% \begin{implementation}
+% 
+% \section{\pkg{groupthm} implementation}
+%
+%    \begin{macrocode}
+%<*package>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%<@@=groupthm>
+%    \end{macrocode}
+%
+%
+%
+%
+% \subsection{Dependencies}
+%
+%
+%
+% First, we import other packages on which we rely on, and
+% set up some private wrappers around these.
+%    \begin{macrocode}
+\RequirePackage{amsthm}
+\RequirePackage{thmtools}
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_thmtools_declare_theorem:nn, \@@_thmtools_declare_theorem:Vn}
+%   \begin{syntax}
+%     \cs{@@_thmtools_declare_theorem:nn} \mymeta{theorem name}\mymeta{thmtools keyval args}
+%   \end{syntax}
+% 
+%  This is just a private wrapper around \cs{declaretheorem} of the \pkg{thmtools} package.
+% 
+%    \begin{macrocode}
+\cs_new:Npn \@@_thmtools_declare_theorem:nn #1 #2
+{
+  \tl_log:n { Declaring ~ thmtools ~ theorem ~ #2 }
+  \declaretheorem [ #1 ] { #2 }
+}
+\cs_generate_variant:Nn \@@_thmtools_declare_theorem:nn { V n }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% It also comes in handy to have a stronger version of the 
+% hook role setting mechanism:
+% \begin{macro}{\@@_hook_gset_rule_foreach:nNnn}
+%    \begin{syntax}
+%       \cs{@@_hook_gset_rule_foreach:nNnn}\marg{hook}\mymeta{clist name}\mymeta{relation}\mymeta{label}
+%    \end{syntax}
+%		 
+%   This is a wrapper around the \cs{hook_gset_rule:nnnn} macro
+%   that takes a clist name of labels, and executes the corresponding
+%   command for each such label.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_hook_gset_rule_foreach:nNnn #1 #2 #3 #4
+  {
+    \cs_set:Npn \@@_map_aux:n ##1
+    {
+      \hook_gset_rule:nnnn { #1 } { ##1 } { #3 } { #4 }
+    }
+    \clist_map_function:NN #2 \@@_map_aux:n
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \subsection{Messages}
+% These are  messages that we might emit.
+%
+% When an unknown group is used somwhere:
+%    \begin{syntax}
+%      \cs{msg_error:nnn}\{ groupthm \}\{ unknown group \}\marg{groupname}
+%    \end{syntax}
+%    \begin{macrocode}
+\msg_new:nnn { groupthm } { unknown ~ group }
+{
+  Unknown  ~ group ~ '#1' ~ supplied ~ \msg_line_context:
+}
+%    \end{macrocode}
+%
+% When an unknown key has been used:
+% \begin{syntax}
+%   \cs{msg_error:nnn}\{ groupthm \}\{ unknown key \}\marg{key}
+% \end{syntax}
+%    \begin{macrocode}
+\msg_new:nnn { groupthm } { unknown ~ key }
+{
+  Unknown ~  key ~ '#1' ~ supplied ~ \msg_line_context:
+}
+%    \end{macrocode}
+%
+% Some data structure is already defined or not defined yet.
+% \begin{syntax}
+%   \cs{msg_error:nnnnn}\{ groupthm \}\{ wrong definition \}
+%   \marg{type}\marg{name}\marg{already $\|$ not}
+% \end{syntax}
+%    \begin{macrocode}
+\msg_new:nnn { groupthm } { wrong ~ definition }
+{
+  Bad ~ definition ~ of ~ #1 ~ '#2' ~ \msg_line_context:, ~ #1 ~ is ~ #3 ~ defined.
+}
+%    \end{macrocode}
+%
+% 
+% When the special \cs{AddTheoremToGroup} macro is issued outside a theorem family options
+% body.
+% \begin{syntax}
+%   \cs{msg_error:nn} \{ groupthm \}\{ misuse add theorem to group \}
+% \end{syntax}
+%    \begin{macrocode}
+\msg_new:nnn { groupthm } { misuse ~ add ~ theorem ~ to ~ group }
+  {
+    Bad ~ usage ~ of ~ 'AddTheoremToGroup' ~ macro ~ outside ~ theorem ~
+    family ~ options ~ \msg_line_context:
+  }
+%    \end{macrocode}
+% 
+% 
+% 
+%  When a theorem family is invoked, but has not been generated yet.
+% \begin{syntax}
+%   \cs{msg_error:nn} \{ groupthm \}\{ undefined theorem variant \}
+% \end{syntax}
+%    \begin{macrocode}
+\msg_new:nnnn { groupthm } { undefined ~ theorem ~ variant }
+  {
+    Bad ~ call ~ of ~ theorem ~ variant ~ of ~ '#1' ~ \msg_line_context:
+  }
+  {
+    You ~ wanted ~ to ~ call ~ the ~ variant ~ with ~ group(s) ~
+    '#2' ~ of ~ theorem ~ family ~ '#1', ~ but ~ it ~ has ~ not ~ been ~
+    generated ~ yet. ~
+    Probably ~ you ~ forgot ~ this. ~
+    \msg_see_documentation_text:n { groupthm }
+  }
+%    \end{macrocode}
+%
+% \subsection{Allocation and initialization}
+%
+% We use hooks at several places. However, these are not intended for outer use,
+% and we thus mark them with a preceding \texttt{__}.
+%
+%    \begin{macrocode}
+\hook_new:n { @@/prefix   }
+\hook_new:n { @@/suffix  }
+\hook_new:n { @@/mapname   }
+\hook_new:n { @@/thmtools  }
+%    \end{macrocode}
+%    \begin{macrocode}
+\hook_new:n { @@/groupsort }
+%    \end{macrocode}
+%
+% \begin{macro}{\hook_gset_rule:nnVn}
+%    \begin{syntax}
+%       \cs{hook_gset_rule:nnVn}\marg{hook}\marg{label 1}\marg{relation}\marg{label 2}
+%    \end{syntax}
+%
+%		 Just a variant of the usual \cs{hook_gset_rule:nnnn} macro that we use.
+%
+%    \begin{macrocode}
+\cs_generate_variant:Nn \hook_gset_rule:nnnn { n n V n }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+%
+% \begin{variable}
+% {
+%   \l_@@_key_prefix_tl, \l_@@_key_name_tl, \l_@@_key_suffix_tl,
+%   \l_@@_key_group_clist, \l_@@_key_mapname_clist, \l_@@_key_thmtools_clist
+% }
+% These variables will be set by the key-value interface provided by
+% \pkg{l3keys} and are used in various places in the package.
+%    \begin{macrocode}
+\tl_new:N    \l_@@_key_prefix_tl
+\tl_new:N    \l_@@_key_name_tl
+\tl_new:N    \l_@@_key_suffix_tl
+\clist_new:N \l_@@_key_group_clist
+\clist_new:N \l_@@_key_mapname_clist
+\clist_new:N \l_@@_key_thmtools_clist
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}
+%   {
+%     \l_@@_prefix_tl,
+%     \l_@@_name_tl,
+%     \l_@@_suffix_tl,
+%     \l_@@_mapname_clist,
+%     \l_@@_thmtools_clist,
+%     \l_@@_group_clist
+%   }
+%
+%   General local variables.
+%   Will typically be used to extract the variables set by the \pkg{l3keys} interface,
+%   but also in just a local variable sense.
+%     
+%    \begin{macrocode}
+\tl_new:N    \l_@@_prefix_tl
+\tl_new:N    \l_@@_name_tl
+\tl_new:N    \l_@@_suffix_tl
+\clist_new:N \l_@@_mapname_clist
+\clist_new:N \l_@@_thmtools_clist
+\clist_new:N \l_@@_group_clist
+%    \end{macrocode}
+% \end{variable}
+% 
+% 
+% 
+% \begin{variable}{\g_@@_defined_theorem_groups_clist}
+%		 
+%     This variable will hold a global list of declared theorem groups
+%
+%    \begin{macrocode}
+\clist_new:N \g_@@_defined_theorem_groups_clist
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\l_@@_in_family_options_environment_bool}
+%  This variable indicates whether we are in the special environment
+%  used to parse a set of groups out of options given to a theorem
+%  family.
+%
+%  This bool toggles the availability of the special \cs{AddTheoremToGroup} macro.
+%    \begin{macrocode}
+\bool_new:N  \l_@@_in_family_options_environment_bool
+%    \end{macrocode}
+% \end{variable}
+% 
+%
+% \subsection{Key interface}
+% As mentioned, all keys will set their corresponding local variables
+% (containing \enquote{\texttt{_key_}} in their name) and store the
+% user input in these.
+% 
+% Additionally, we group these keys by use cases,
+% and provide defaults that in most cases will not require further handling.
+%
+% 
+%
+%    \begin{macrocode}
+\keys_define:nn { groupthm }
+  {
+    prefix      .tl_set:N      = \l_@@_key_prefix_tl,
+    prefix      .default:n     = \c_empty_tl,
+    prefix      .groups:n      = { theoremgroup },
+    name         .tl_set:N      = \l_@@_key_name_tl,
+    name         .default:n     = \c_novalue_tl,
+    name         .groups:n      = { groupedtheorem, theoremvariants },
+    suffix     .tl_set:N      = \l_@@_key_suffix_tl,
+    suffix     .default:n     = \c_empty_tl,
+    suffix     .groups:n      = { theoremgroup },
+    group        .clist_set:N   = \l_@@_key_group_clist,
+    group        .default:n     = {},
+    group        .groups:n      = { groupedtheorem, theoremvariants },
+    mapname      .clist_set:N   = \l_@@_mapname_clist,
+    mapname      .default:n     = {},
+    mapname      .groups:n      = { theoremgroup },
+    thmtools     .clist_set:N   = \l_@@_key_thmtools_clist,
+    thmtools     .default:n     = {},
+    thmtools     .groups:n      =
+      { theoremgroup, groupedtheorem, theoremvariants },
+    unknown      .code:n        =
+      \msg_error:nnn { groupthm } { unknown ~ group } { \l_keys_key_str }
+  }
+%    \end{macrocode}
+% 
+%
+% The only key whose default requires such handling is the \enquote{\texttt{name}} key,
+% which will be set to a capitalized version of the environment name
+% when not specified.
+%
+%
+% \begin{macro}{\@@_set_normalized_keys:nnn}
+%    \begin{syntax}
+%       \cs{@@_set_normalized_keys:nnn}\marg{keys}\marg{key group}\marg{fallback name}
+%    \end{syntax}
+%		 
+% Sets the packages keys and normalizes the retrieved values, that is,
+% clears old set keys, stores all keys in local variables,
+% and replaces the \cs{l_@@_name_tl} with the capitalized version of the
+% \mymeta{fallback name}.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_set_normalized_keys:nnn #1 #2 #3
+  {
+    \keys_set:nn { groupthm } { prefix, name, suffix, group, mapname, thmtools }
+    \keys_set_groups:nnn { groupthm } { #2 } { #1 }
+%    \end{macrocode}
+%
+% Normalize given name
+%
+%    \begin{macrocode}
+    \tl_if_eq:NnTF \l_@@_key_name_tl { \c_novalue_tl }
+      {
+        \tl_set:Nx \l_@@_name_tl
+          {
+            \text_titlecase_first:n {#3}
+          }
+      }
+      {
+        \tl_set_eq:NN \l_@@_name_tl \l_@@_key_name_tl
+      }
+%    \end{macrocode}
+% 
+% Copy set keys into local variables 
+% 
+%    \begin{macrocode}
+    \tl_set_eq:NN    \l_@@_prefix_tl     \l_@@_key_prefix_tl
+    \tl_set_eq:NN    \l_@@_suffix_tl    \l_@@_key_suffix_tl
+    \clist_set_eq:NN \l_@@_group_clist    \l_@@_key_group_clist
+    \clist_set_eq:NN \l_@@_mapname_clist  \l_@@_key_mapname_clist
+    \clist_set_eq:NN \l_@@_thmtools_clist \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \subsection{Theorem groups}
+%
+% For technical reasons explained in the \todoref section, we need to 
+% some arbitrary, but unique total ordering on the set of all defined theorem groups.
+%
+% Since unfortunately (by now) there is no standard mechanism for sorting strings
+% in \LaTeX3 directly, we use an ugly hack to achieve what we want:
+%
+% We will use an internal hook, and apply hook rules to each pair of internal groups
+% such that the resulting relation is a total order.
+% Whenever we want to sort a list of groups now, we do the following:
+% First, for each group element in the list, insert into the hook the function
+% \enquote{put this group back into the list}, using the group itself as a label.
+% Then we clear the list, and finally execute the hook.
+% 
+% Essentially, we thus split up the hook in the single groups, let the \LaTeX3 hook
+% mechanism take care of the sorting, and restore the sorted single pieces into our list.
+% Of course, this is very inefficient, but for now it seems to be the simplest solution,
+% without having to implement an own string sorting function.
+% 
+% Once there is such a proper mechanism, the author will likely update this to proper
+% string sorting.
+%
+% \begin{macro}{\@@_add_to_theorem_group_ordering:n}
+%    \begin{syntax}
+%       \cs{@@_add_to_theorem_group_ordering:n}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    Sets hook relations for this group and all already defined theorem groups.     
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_add_to_theorem_group_ordering:n #1
+  {
+    \@@_hook_gset_rule_foreach:nNnn
+      { @@/groupsort }
+      \g_@@_defined_theorem_groups_clist
+      { before }
+      { #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% 
+% 
+% \begin{macro}{\@@_remove_from_theorem_group_ordering:n}
+%    \begin{syntax}
+%       \cs{@@_remove_from_theorem_group_ordering:n}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    Removes all relations of this theorem group with the currently defined theorem groups.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_remove_from_theorem_group_ordering:n #1
+  {
+    \@@_hook_gset_rule_foreach:nNnn
+      { @@/groupsort }
+      \g_@@_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\@@_add_to_sort_hook:n}
+%    \begin{syntax}
+%       \cs{@@_add_to_sort_hook:n}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    Adds the theorem group into the sort hook to be restored later from it.
+%    This already uses the assumption, that we want to use the \cs{l_@@_group_clist}
+%    variable (which we do).
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_add_to_sort_hook:n #1
+{
+  \hook_gput_code:nnn { @@/groupsort }
+  { #1 }
+  {
+    \clist_put_left:Nn \l_@@_group_clist { #1 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\@@_sort_theorem_group_names:}
+%		 
+%     As explained briefly before, we first insert all theorems
+%     into the hook, clear the list, and then use the hook again.
+%     
+%     This then sorts the \cs{l_@@_group_clist} variable,
+%     which is also assumed to hold only defined theorem group names.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_sort_theorem_group_names:
+  {
+    \hook_gremove_code:nn { @@/groupsort  }{*}
+    \clist_map_function:NN \l_@@_group_clist \@@_add_to_sort_hook:n
+    \clist_clear:N \l_@@_group_clist
+    \hook_use:n { @@/groupsort }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\@@_define_group_aux:nnnnn}
+%    \begin{syntax}
+%       \cs{@@_define_group_aux:nnnnn}\marg{theorem group}\marg{prefix tl}
+%       \marg{suffix tl}\marg{mapname clist}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+% This creates a new theorem group out of the given parameters.
+% We store all given contents in our (private) hooks, using the group name as the key
+% so that we can later retrieve the components of each group separately.
+%
+% This is an internal function and assumes that the group is currently not defined,
+% and also removed from all hooks.
+%
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_define_group_aux:nnnnn #1#2#3#4#5
+  {
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_use_group_\meta{theorem group}:}
+%
+% This is the internal macro that will be called when retrieving contents of a group.
+% We define this here to store the properties of the group.
+%
+%    \begin{macrocode}
+  \cs_new:cpn { @@_use_group_#1: }
+    {
+      \hook_gput_code:nnn { @@/prefix } { #1 }
+        {
+            \tl_put_left:Nx \l_@@_prefix_tl { #2 }
+        }
+      \hook_gput_code:nnn { @@/suffix } { #1 }
+        {
+            \tl_put_right:Nx \l_@@_suffix_tl { #3 }
+        }
+      \hook_gput_code:nnn { @@/mapname } { #1 }
+        {
+          \clist_put_right:Nn \l_@@_mapname_clist { #4 }
+        }
+      \hook_gput_code:nnn { @@/thmtools } { #1 }
+        {
+          \clist_put_right:Nn \l_@@_thmtools_clist { #5 }
+        }
+    }
+%    \end{macrocode}
+% \end{macro}
+%
+% This ensures the ordering hacks explained before.
+%
+%    \begin{macrocode}
+    \@@_add_to_theorem_group_ordering:n { #1 }
+%    \end{macrocode}
+%
+% Add defined group to corresponding list 
+%
+%    \begin{macrocode}
+    \clist_gput_left:Nn \g_@@_defined_theorem_groups_clist { #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\@@_undefine_group_aux:n}
+%    \begin{syntax}
+%       \cs{@@_undefine_group_aux:n}\marg{theorem group}
+%    \end{syntax}
+%		 
+% Undeclares / undefines the given theorem group.
+% This means removing its hook code in the \texttt{prefix}, \texttt{suffix},
+% \texttt{mapname} and \texttt{thmtools} hooks,
+% and removing all relations with other theorem groups globally
+% as well as for each hook individually.
+%
+% This macro assumes that the group was defined prior to calling.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_undefine_group_aux:n #1
+  {
+    \cs_undefine:c { @@_use_group_#1:   }
+%    \end{macrocode}
+% 
+% Remove properties from hooks
+%
+%    \begin{macrocode}
+    \hook_gremove_code:nn { @@/prefix  } { #1 }
+    \hook_gremove_code:nn { @@/suffix } { #1 }
+    \hook_gremove_code:nn { @@/mapname  } { #1 }
+    \hook_gremove_code:nn { @@/thmtools } { #1 }
+%    \end{macrocode}
+%
+% Remove theorem group from list of defined theorems
+%
+%    \begin{macrocode}
+    \clist_gremove_all:Nn  \g_@@_defined_theorem_groups_clist { #1 }
+%    \end{macrocode}
+%
+% Now, unset all relations with all defined theorem groups in the internal hooks.
+%
+%    \begin{macrocode}
+    \@@_hook_gset_rule_foreach:nNnn
+      { ?? }
+      \g_@@_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \@@_hook_gset_rule_foreach:nNnn
+      { @@/prefix }
+      \g_@@_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \@@_hook_gset_rule_foreach:nNnn
+      { @@/suffix }
+      \g_@@_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \@@_hook_gset_rule_foreach:nNnn
+      { @@/mapname }
+      \g_@@_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \@@_hook_gset_rule_foreach:nNnn
+      { @@/thmtools }
+      \g_@@_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+%    \end{macrocode}
+%
+% Also clear all sorting relations
+%
+%    \begin{macrocode}
+    \@@_remove_from_theorem_group_ordering:n { #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% With these two helper functions, we can now easily implement the
+% \texttt{new}, \texttt{renew}, \texttt{provide} and \texttt{declare} variants
+% of the theorem group macro:
+% 
+% \begin{macro}{\groupthm_new_theorem_group:nnnnn, \groupthm_new_theorem_group:nVVVV}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \@@_define_aux:nnnNNNn #1 #2 #3 #4 #5 #6 #7
+{
+  \bool_if:nT
+    {
+      \str_if_eq_p:nn { #1 } { new }
+      &&
+      \cs_if_exist_p:N #4
+    }
+    {
+          \msg_error:nnnn { groupthm } { wrong ~ definition }
+            { #2 } { #3 } { already }
+    }
+
+    \bool_if:nT
+    {
+      \str_if_eq_p:nn { #1 } { renew }
+      &&
+      ! \cs_if_exist_p:N #4
+    }
+    {
+        \msg_error:nnnn { groupthm } { wrong ~ definition }
+          { #2 } { #3 } { not }
+    }
+
+    \bool_if:nT
+    {
+      (
+        \str_if_eq_p:nn { #1 } { declare } ||
+        \str_if_eq_p:nn { #1 } { renew } 
+      ) &&
+      \cs_if_exist_p:N #4
+    }
+    {
+        #5 { #1 }
+    }
+
+    #6 #7
+}
+\cs_generate_variant:Nn \@@_define_aux:nnnNNNn { n n n c N N n }
+
+\cs_new:Npn \@@_define_list_aux:nnnNNnn #1 #2 #3 #4 #5 #6 #7
+{
+  \cs_set:Npn \@@_map_aux:n ##1
+  {
+    \cs_new:cn { #6 }
+    {
+      \@@_define_aux:nnncNNn
+        { ##1 }
+        { #2 }
+        { ####1 }
+        { #3 }
+        #4
+        #5
+        {
+          #7
+        }
+    }
+  }
+  \cs_show:N \@@_map_aux:n
+
+  \clist_map_function:nN { #1 } \@@_map_aux:n
+}
+
+
+\@@_define_list_aux:nnnNNnn
+  { new, renew, provide, declare }
+  { theorem group }
+  { @@_use_group_##1: }
+  \@@_undefine_group_aux:n
+  \@@_define_group_aux:nnnnn
+  { groupthm_#1_group:nnnnn }
+  { { ##1 } { ##2 } { ##3 } { ##4 } { ##5 } }
+%    \end{macrocode}
+%
+% Finally, generate some extra variant.
+%
+%    \begin{macrocode}
+\cs_generate_variant:Nn \groupthm_new_theorem_group:nnnnn { n V V V V }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+
+%    \end{macrocode}
+% 
+% 
+% 
+% With the \cs{@@_set_normalized_keys:nnn} macro at hand,
+% it is also easy to provide key-value interfaces for these commands:
+%
+% \begin{macro}{\groupthm_new_theorem_group_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_group_from_keys:nn #1#2
+{
+  \@@_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_new_theorem_group:nVVVV { #2 }
+    \l_@@_prefix_tl
+    \l_@@_suffix_tl
+    \l_@@_mapname_clist
+    \l_@@_thmtools_clist
+}
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\groupthm_renew_theorem_group_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_renew_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_renew_theorem_group_from_keys:nn #1#2
+{
+  \@@_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_renew_theorem_group:nVVVV { #2 }
+    \l_@@_prefix_tl
+    \l_@@_suffix_tl
+    \l_@@_mapname_clist
+    \l_@@_thmtools_clist
+}
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\groupthm_provide_theorem_group_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_group_from_keys:nn #1#2
+{
+  \@@_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_provide_theorem_group:nVVVV { #2 }
+    \l_@@_prefix_tl
+    \l_@@_suffix_tl
+    \l_@@_mapname_clist
+    \l_@@_thmtools_clist
+}
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\groupthm_declare_theorem_group_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_declare_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_declare_theorem_group_from_keys:nn #1#2
+{
+  \@@_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_declare_theorem_group:nVVVV { #2 }
+    \l_@@_prefix_tl
+    \l_@@_suffix_tl
+    \l_@@_mapname_clist
+    \l_@@_thmtools_clist
+}
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%  Finally, we provide \LaTeX2e wrappers as document commands for these.
+%
+%
+% \begin{macro}{\NewTheoremGroup}
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\NewTheoremGroup}{ O{} m }
+  {
+    \groupthm_new_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\RenewTheoremGroup}
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\RenewTheoremGroup}{ O{} m }
+  {
+    \groupthm_renew_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\ProvideTheoremGroup}
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\ProvideTheoremGroup}{ O{} m }
+  {
+    \groupthm_provide_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\DeclareTheoremGroup}
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\DeclareTheoremGroup}{ O{} m }
+  {
+    \groupthm_declare_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% We also provide the interface for declaring the precedence rules for theorem groups.
+%
+%
+% \begin{macro}{\groupthm_declare_theorem_group_rule:nnnn}
+%    \begin{syntax}
+%       \cs{groupthm_declare_theorem_group_rule:nnnn}\marg{keyname}\marg{theorem group 1}
+%       \marg{relation}\marg{theorem group 2}
+%    \end{syntax}
+%		 
+% We have to normalize the arguments a little bit, namely replacing \texttt{higher}
+% and \texttt{lower} with \texttt{before} \texttt{after} respectively,
+% and prefix the \mymeta{keyname} with \texttt{__groupthm}
+% in case it is not the general hook \enquote{\texttt{??}}.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_declare_theorem_group_rule:nnnn #1 #2 #3 #4
+  {
+    \str_set:Nx \l_tmpa_str { \tl_trim_spaces:n { #3 } }
+
+    \str_if_eq:VnT \l_tmpa_str { higher }
+    {
+      \str_set:Nn \l_tmpa_tl { after }
+    }
+
+    \str_if_eq:VnT \l_tmpa_str { lower }
+    {
+      \str_set:Nn \l_tmpa_tl { before }
+    }
+
+    \str_if_eq:nnTF { #1 } { ?? }
+    {
+      \hook_gset_rule:nnVn {??} {#2} \l_tmpa_tl {#4}
+    }
+    {
+      \hook_gset_rule:nnVn { @@ / #1 } {#2} \l_tmpa_tl {#4}
+    }
+  }
+%    \end{macrocode}
+% \end{macro}
+
+% \begin{macro}{\DeclareTheoremGroupRule}
+%    \begin{syntax}
+%      \cs{DeclareTheoremGroupRule}\oarg{keyname}%
+%      \marg{theorem group 1}\marg{relation}\marg{theorem group 2}
+%    \end{syntax}
+%
+%    \begin{macrocode}
+\NewDocumentCommand { \DeclareTheoremGroupRule } { O{??} m m m }
+  {
+    \groupthm_declare_theorem_group_rule:nnnn {#1} {#2} {#3} {#4}
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+  % \subsection{Iterating over powersets}
+% For generating the different variants of a theorem family,
+% we need to iterate over over the powerset of some list.
+% This is a collection of hacks that perform exactly this,
+% but these are poorly documented for now.
+% 
+%
+% \begin{macro}{\@@_powerset_clist_foreach:Nn}
+%    \begin{syntax}
+%       \cs{@@_powerset_clist_foreach:Nn}\mymeta{clist}\marg{code}
+%    \end{syntax}
+%		 
+%   Executes \mymeta{code} for each subset of the given clist variable.
+%   The value of the (local) variable is changes throughout the iteration,
+%   and is thus available regularly in \mymeta{code}.
+%   Its value is restored at the end of the iteration.
+%
+%    \begin{macrocode}
+\clist_new:N  \l__powerset_copied_clist
+\seq_new:N    \l__powerset_saved_seq
+\cs_generate_variant:Nn \clist_remove_all:Nn { N V }
+\cs_new:Npn \__powerset_clist_foreach_aux:Nn #1 #2 
+  {
+    \clist_if_empty:NTF \l__powerset_copied_clist
+      {
+        #2
+      }
+      {
+        \clist_get:NN \l__powerset_copied_clist \l_tmpa_tl
+        \seq_push:NV  \l__powerset_saved_seq \l_tmpa_tl
+        \clist_pop:NN \l__powerset_copied_clist { \l_tmpa_tl }
+
+        \__powerset_clist_foreach_aux:Nn #1 {#2}
+        
+        \seq_get:NN \l__powerset_saved_seq \l_tmpa_tl
+        \clist_put_left:NV #1 \l_tmpa_tl
+
+        \__powerset_clist_foreach_aux:Nn #1 {#2}
+
+        \seq_get:NN \l__powerset_saved_seq \l_tmpa_tl
+        \clist_remove_all:NV #1 \l_tmpa_tl
+        \clist_push:NV \l__powerset_copied_clist \l_tmpa_tl
+        \seq_pop:NN \l__powerset_saved_seq \l_tmpa_tl
+      }
+  }
+\cs_new:Npn \powerset_clist_foreach:Nn #1 #2
+  {
+    \clist_set_eq:NN \l__powerset_copied_clist #1
+    \clist_clear:N #1
+    \clist_remove_duplicates:N \l__powerset_copied_clist
+    \__powerset_clist_foreach_aux:Nn #1 {#2}
+    \clist_set_eq:NN #1 \l__powerset_copied_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% 
+% \subsection{Grouped Theorems} 
+% 
+% 
+% \begin{macro}{\@@_use_theorem_group:n}
+%    \begin{syntax}
+%       \cs{@@_use_theorem_group:n}\mymeta{theorem group}
+%    \end{syntax}
+%		 
+%    Uses this theorem group, i.e.~applies its definition by writing
+%    to the internal hooks.
+%    A proper error message is emitted if the group is not defined.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_use_theorem_group:n #1
+  {
+    \cs_if_exist_use:cF { @@_use_group_#1: }
+    {
+      \msg_error:nnn { groupthm } { unknown ~ group } { #1 }
+    }
+  }
+%    \end{macrocode}
+% \end{macro} 
+%
+% 
+%
+% \begin{macro}{\@@_use_function_on_name:n}
+%    \begin{syntax}
+%       \cs{@@_use_function_on_name:n}\mymeta{function}
+%    \end{syntax}
+%		 
+%    The \mymeta{function} is expected to be of type \texttt{:n},
+%    This applies the function to the \cs{l_@@_name_tl}
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_use_function_on_name:n #1
+  {
+    \tl_set:Nx \l_@@_name_tl
+      {
+        #1 { \tl_use:N \l_@@_name_tl }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\@@_declare_grouped_theorem_aux:nnnn}
+%    \begin{syntax}
+%       \cs{@@_declare_grouped_theorem_aux:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%   This is the internal backend that declares a grouped theorem
+%   by retrieving all the group properties and issuing a (single) \cs{declaretheorem}
+%   command of \pkg{thmtools}.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_declare_grouped_theorem_aux:nnnn #1 #2 #3 #4
+  {
+%    \end{macrocode}
+% First, set local variables to default values and store current name.
+%    \begin{macrocode}
+    \tl_clear:N     \l_@@_prefix_tl
+    \tl_set:Nn      \l_@@_name_tl        { #3 }
+    \tl_clear:N     \l_@@_suffix_tl
+    \clist_clear:N  \l_@@_mapname_clist
+    \clist_clear:N  \l_@@_thmtools_clist
+%    \end{macrocode}
+% Clear all hooks
+%    \begin{macrocode}
+    \hook_gremove_code:nn { @@/prefix  }{*}
+    \hook_gremove_code:nn { @@/suffix }{*}
+    \hook_gremove_code:nn { @@/mapname  }{*}
+    \hook_gremove_code:nn { @@/thmtools }{*}
+%    \end{macrocode}
+% Now, retrieve the group properties, by writing these into the hooks
+%    \begin{macrocode}
+    \clist_map_function:nN { #2 } \@@_use_theorem_group:n
+%    \end{macrocode}
+% Execute the hooks, so that local variables will get modified according to the groups
+% and in the order that were specified for the hooks.
+%    \begin{macrocode}
+    \hook_use:n { @@/prefix }
+    \hook_use:n { @@/suffix }
+    \hook_use:n { @@/mapname }
+    \hook_use:n { @@/thmtools }
+%    \end{macrocode}
+% We are left with dealing with the obtained data.
+% We first map on the name, before appending to it.
+%    \begin{macrocode}
+    \clist_map_function:NN \l_@@_mapname_clist \map_use_on_name:n
+%    \end{macrocode}
+% We now glue the name together of its three parts,
+% and pass this key directly to the \pkg{thmtools} arguments
+%    \begin{macrocode}
+    \clist_put_right:Nx \l_@@_thmtools_clist
+      {
+        name = \tl_use:N \l_@@_prefix_tl
+               \tl_use:N \l_@@_name_tl
+               \tl_use:N \l_@@_suffix_tl
+      }
+%    \end{macrocode}
+% Finally, apply the additional \pkg{thmtools} keys for this specific theorem.
+% Putting them last will overwrite keys that were given by the groups.
+%    \begin{macrocode}
+    \clist_put_right:Nn \l_@@_thmtools_clist { #4 }
+%    \end{macrocode}
+% We can now pass our list to \pkg{thmtools}, declaring the theorem.
+%    \begin{macrocode}
+    \@@_thmtools_declare_theorem:Vn
+      \l_@@_thmtools_clist
+      { #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% As usual, we provide a \texttt{new} and a \texttt{provide} variant wrapped
+% around this that do proper error checking.
+% 
+% 
+%
+% \begin{macro}
+% {
+%   \groupthm_new_grouped_theorem:nnnn,
+%   \groupthm_new_grouped_theorem:nVVV,
+%   \groupthm_new_grouped_theorem:xVnn
+% }
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem:nnnn #1 #2 #3 #4
+  {
+%    \end{macrocode}
+% Note that the next comparison depends on \pkg{thmtools} declaring
+% environments, and that \LaTeX\ handles environments called with the
+% |\begin{environment}| syntax by calling |\environment| subsequently.
+%    \begin{macrocode}
+    \cs_if_exist:cTF { #1 }
+      {
+        \msg_error:nnnnn { groupthm } { wrong ~ definition }
+          { grouped ~ theorem } { #1 } { already }
+      }
+      {
+        \@@_declare_grouped_theorem_aux:nnnn
+          { #1 } { #2 } { #3 } { #4 }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_new_grouped_theorem:nnnn { n V V V }
+%    \end{macrocode}
+% We need this extra variant here for the generation of theorem families later:
+%    \begin{macrocode}
+\cs_generate_variant:Nn \groupthm_new_grouped_theorem:nnnn { x V n n }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\groupthm_provide_grouped_theorem:nnnn,\groupthm_provide_grouped_theorem:nVVV}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem:nnnn #1 #2 #3 #4
+  {
+%    \end{macrocode}
+% Note that the next comparison depends on \pkg{thmtools} declaring
+% environments, and that \LaTeX\ handles environments called with the
+% |\begin{environment}| syntax by calling |\environment| subsequently.
+%    \begin{macrocode}
+    \cs_if_exist:cF { #1 }
+      {
+        \@@_declare_grouped_theorem_aux:nnnn
+          { #1 } { #2 } { #3 } { #4 }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_provide_grouped_theorem:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+%   The star variants of these that add the \texttt{unnumbered} group
+%   are straightforward:
+%
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_star:nnnn}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_new_grouped_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+% 
+% \begin{macro}{\groupthm_provide_grouped_theorem_star:nnnn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_star:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_provide_grouped_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%  
+% On top of these, we can provide the shorter versions that will generate
+% two theorems each, one with and one without a \enquote{*} in its 
+% environment name
+% 
+% 
+% 
+% \begin{macro}{\groupthm_new_theorem:nnnn,\groupthm_new_theorem:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem:nnnn #1 #2 #3 #4
+  {
+    \groupthm_new_grouped_theorem:nnnn
+      { #1 } { #2 } { #3 } { #4 }
+    \groupthm_new_grouped_theorem:nnnn
+      { #1* } { #2, starred } { #3 } { #4 }
+  }
+\cs_generate_variant:Nn \groupthm_new_theorem:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\groupthm_provide_theorem:nnnn,\groupthm_provide_theorem:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem:nnnn #1 #2 #3 #4
+  {
+    \groupthm_provide_grouped_theorem:nnnn
+      { #1 } { #2 } { #3 } { #4 }
+    \groupthm_provide_grouped_theorem:nnnn
+      { #1* } { #2, starred } { #3 } { #4 }
+  }
+\cs_generate_variant:Nn \groupthm_provide_theorem:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% Combining these is also not difficult:
+% 
+% 
+% 
+% 
+% \begin{macro}{\groupthm_new_theorem_star:nnnn}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_star:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_new_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+% 
+% \begin{macro}{\groupthm_provide_theorem_star:nnnn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_star:nnnn}\marg{environment name}
+%       \marg{groups clist}\marg{theorem name}\marg{thmtools keys}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_provide_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% We now provide the corresponding key-valued interfaces around these.
+% All of these work in the same way:
+% We set the normalized keys, and then pass these by value to the
+% previously defined macros
+% 
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_grouped_theorem:nVVV
+      { #1 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_provide_grouped_theorem_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_grouped_theorem:nVVV
+      { #1 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_star_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_grouped_theorem_star:nVVV
+      { #2 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_provide_grouped_theorem_star_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_grouped_theorem_star:nVVV
+      { #2 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\groupthm_new_theorem_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_theorem:nVVV
+      { #2 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_provide_theorem_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_theorem:nVVV
+      { #2 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_new_theorem_star_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_theorem_star:nVVV
+      { #1 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_provide_theorem_star_from_keys:nn}
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_theorem_star:nVVV
+      { #1 }
+      \l_@@_key_group_clist
+      \l_@@_name_tl
+      \l_@@_key_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%  
+%
+% Now, we can wrap these into document commands
+% 
+%
+% \begin{macro}{\NewGroupedTheorem, \NewGroupedTheorem*}
+%    \begin{syntax}
+%       \cs{NewGroupedTheorem}\oarg{keys}\marg{theorem name}
+%    \end{syntax}
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\NewGroupedTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_new_grouped_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_new_grouped_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\ProvideGroupedTheorem, \ProvideGroupedTheorem*}
+%    \begin{syntax}
+%       \cs{ProvideGroupedTheorem}\oarg{keys}\marg{theorem name}
+%    \end{syntax}
+%
+%    \begin{macrocode}
+\ProvideDocumentCommand{\NewGroupedTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_provide_grouped_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_provide_grouped_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\NewTheorem, \NewTheorem*}
+%    \begin{syntax}
+%       \cs{NewTheorem}\oarg{keys}\marg{theorem name}
+%    \end{syntax}
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\NewTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_new_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_new_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\ProvideTheorem, \ProvideTheorem*}
+%    \begin{syntax}
+%       \cs{ProvideTheorem}\oarg{keys}\marg{theorem name}
+%    \end{syntax}
+%
+%    \begin{macrocode}
+\ProvideDocumentCommand{\NewTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_provide_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_provide_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% 
+% \subsection{Theorem families}
+%
+%
+% We now want to implement the generation of theorem families and their
+% corresponding options.
+% As a backend, we use the following auxiliary function
+% 
+%
+% \begin{macro}{\@@_declare_grouped_theorem_family_aux:nnnnnn}
+%    \begin{syntax}
+%       \cs{@@_declare_grouped_theorem_family_aux:nnnnnn}\marg{family name}\marg{groups clist}
+%       \marg{name}\marg{name}\marg{thmtools clist}\marg{extra groups clist}\marg{generation type}
+%    \end{syntax}
+%		 
+%   This will generate a new grouped theorem for each union of a subset of \mymeta{groups clist}
+%   and the extra set \mymeta{extra groups clist}, with the given properties, that is
+%   the \mymeta{nam} and \mymeta{thmtools clist} will be passed to the grouped theorem.
+%   The \mymeta{theorem name} of the grouped theorem will be an internal name that contains
+%   the \mymeta{family name} and the list of groups of this variant, that will be generated
+%   in a unique manner to later retrieve the generated theorems when parsing theorem families.
+%    
+%  The \mymeta{generation type} can be either \texttt{new} or \texttt{provide},
+%  depending on which backend for grouped theorem generation to use
+%    \begin{macrocode}
+\cs_new:Npn \@@_declare_grouped_theorem_family_aux:nnnnnn #1 #2 #3 #4 #5 #6
+  {
+%    \end{macrocode}
+% Make a local copy of the \mymeta{groups clist} argument,
+% and iterate over its powerset
+%    \begin{macrocode}
+    \clist_set:Nn \l_tmpa_clist { #2 }
+    \powerset_clist_foreach:Nn \l_tmpa_clist
+      {
+%    \end{macrocode}
+% We read out the current value of the list, and append the extra groups
+% This ensures that now \cs{l_@@_group_clist} iterates over the proper subsets
+%    \begin{macrocode}
+        \clist_set_eq:NN \l_@@_group_clist \l_tmpa_clist
+        \clist_put_right:Nn \l_@@_group_clist { #5 }
+%    \end{macrocode}
+% This sorting is necessary so that for each theorem family and set of groups,
+% the generated name will be unique:
+%    \begin{macrocode}
+        \@@_sort_theorem_group_names:
+%    \end{macrocode}
+% Now just declare the grouped theorem, passing the corresponding arguments and using
+% specified \texttt{\#6} as backend.
+%    \begin{macrocode}
+        \use:c{groupthm_#6_grouped_theorem:xVnn}
+          {__#1__groups_\clist_use:Nn \l_@@_group_clist {_}}
+          \l_@@_group_clist
+          { #3 }
+          { #4 }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_family:nnnn,\groupthm_new_grouped_theorem_family:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem_family:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%    Just pass the arguments to the auxiliary function, with no additional groups
+%    and the \texttt{new} backend.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_family:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2 } { #3 } { #4 } { } { new }
+  }
+\cs_generate_variant:Nn \groupthm_new_grouped_theorem_family:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_grouped_theorem_family:nnnn,\groupthm_provide_grouped_theorem_family:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_family:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%    Just pass the arguments to the auxiliary function, with no additional groups
+%    and the \texttt{provide} backend.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_family:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2 } { #3 } { #4 } { } { provide }
+  }
+\cs_generate_variant:Nn \groupthm_provide_grouped_theorem_family:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% The starred variants that add the \texttt{unnumbered} group are straightforward:
+% 
+% 
+% 
+% \begin{macro}{\groupthm_new_grouped_theorem_family_star:nnnn,\groupthm_new_grouped_theorem_family_star:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem_family_star:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%    Just pass the arguments to the auxiliary function, with the additional
+%    \texttt{unnumbered group} and the \texttt{new} backend.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_family_star:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2 } { #3 } { #4 } { unnumbered } { new }
+  }
+\cs_generate_variant:Nn \groupthm_new_grouped_theorem_family_star:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_grouped_theorem_family_star:nnnn,\groupthm_provide_grouped_theorem_family_star:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_family_star:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%    Just pass the arguments to the auxiliary function, with the additional
+%    \texttt{unnumbered group} and the \texttt{provide} backend.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_family_star:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2 } { #3 } { #4 } { } { provide }
+  }
+\cs_generate_variant:Nn \groupthm_provide_grouped_theorem_family_star:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% Now define the variants that also generate the starred and unstarred family versions.
+% 
+% 
+% \begin{macro}{\groupthm_new_theorem_family:nnnn,\groupthm_new_theorem_family:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_family:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_family:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2, starred } { #3 } { #4 } { } { new }
+  }
+\cs_generate_variant:Nn \groupthm_new_theorem_family:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_theorem_family:nnnn,\groupthm_provide_theorem_family:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_family:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_family:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2, starred } { #3 } { #4 } { } { provide }
+  }
+\cs_generate_variant:Nn \groupthm_provide_theorem_family:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\groupthm_new_theorem_family_star:nnnn,\groupthm_new_theorem_family_star:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_family_star:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_family_star:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2, starred } { #3 } { #4 } { unnumbered } { new }
+  }
+\cs_generate_variant:Nn \groupthm_new_theorem_family_star:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_theorem_family_star:nnnn,\groupthm_provide_theorem_family_star:nVVV}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_family_star:nnnn}\marg{family name}
+%       \marg{groups}\marg{name}\marg{thmtools clist}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_family_star:nnnn #1 #2 #3 #4
+  {
+    \@@_declare_grouped_theorem_family_aux:nnnnnn
+      { #1 } { #2, starred } { #3 } { #4 } { } { provide }
+  }
+\cs_generate_variant:Nn \groupthm_provide_theorem_family_star:nnnn { n V V V }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% We now make the key variants available of these, all of the work in the same way
+% as we just have to set the normalized keys and pass to our non-key-value versions.
+%  
+% 
+% 
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_family_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem_family_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_family_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+    \groupthm_new_grouped_theorem_family:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_grouped_theorem_family_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_family_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_family_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } {groupedtheorem} { #2 }
+    \groupthm_provide_grouped_theorem_family:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_family_star_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem_family_star_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_family_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem }{ #2 }
+    \groupthm_new_grouped_theorem_family_star:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_grouped_theorem_family_star_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_family_star_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_family_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem }{ #2 }
+    \groupthm_provide_grouped_theorem_family_star:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\groupthm_new_theorem_family_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_family_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_family_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+    \groupthm_new_theorem_family:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_theorem_family_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_family_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_family_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+    \groupthm_provide_theorem_family:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_new_theorem_family_star_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_family_star_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_family_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+    \groupthm_new_theorem_family_star:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\groupthm_provide_theorem_family_star_from_keys:nn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_family_star_from_keys:nn}\marg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%   Just retrieve the normalized keys and pass on arguments.
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_family_star_from_keys:nn #1 #2
+  {
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+    \groupthm_provide_theorem_family_star:nVVV
+      { #2 }
+      \l_@@_group_clist
+      \l_@@_name_tl
+      \l_@@_thmtools_clist
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% Finally, we can provide document commands that make these available.
+% 
+%
+% \begin{macro}{\NewGroupedTheoremFamily,\NewGroupedTheoremFamily*}
+%    \begin{syntax}
+%       \cs{NewGroupedTheoremFamily}\oarg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%     
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\NewGroupedTheoremFamily}{s O{} m}
+  {
+    \IfBooleanTF { #1 }
+      {
+        \groupthm_new_grouped_theorem_family_star_from_keys:nn { #2 } { #3 }
+      }
+      {
+        \groupthm_new_grouped_theorem_family_from_keys:nn { #2 } { #3 }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\ProvideGroupedTheoremFamily,\ProvideGroupedTheoremFamily*}
+%    \begin{syntax}
+%       \cs{ProvideGroupedTheoremFamily}\oarg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%     
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\ProvideGroupedTheoremFamily}{s O{} m}
+  {
+    \IfBooleanTF { #1 }
+      {
+        \groupthm_provide_grouped_theorem_family_star_from_keys:nn { #2 } { #3 }
+      }
+      {
+        \groupthm_provide_grouped_theorem_family_from_keys:nn { #2 } { #3 }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \begin{macro}{\NewTheoremFamily,\NewTheoremFamily*}
+%    \begin{syntax}
+%       \cs{NewTheoremFamily}\oarg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%     
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\NewTheoremFamily}{s O{} m}
+  {
+    \IfBooleanTF { #1 }
+      {
+        \groupthm_new_theorem_family_star_from_keys:nn { #2 } { #3 }
+      }
+      {
+        \groupthm_new_theorem_family_from_keys:nn { #2 } { #3 }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+%
+% \begin{macro}{\ProvideTheoremFamily,\ProvideTheoremFamily*}
+%    \begin{syntax}
+%       \cs{ProvideTheoremFamily}\oarg{keys}\marg{family name}
+%    \end{syntax}
+%		 
+%     
+%
+%    \begin{macrocode}
+\NewDocumentCommand{\ProvideTheoremFamily}{s O{} m}
+  {
+    \IfBooleanTF { #1 }
+      {
+        \groupthm_provide_theorem_family_star_from_keys:nn { #2 } { #3 }
+      }
+      {
+        \groupthm_provide_theorem_family_from_keys:nn { #2 } { #3 }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+% \subsection{Theorem family options}
+% 
+% 
+%
+% \begin{macro}{\groupthm_add_theorem_to_group:n}
+%    \begin{syntax}
+%       \cs{groupthm_add_theorem_to_group:n}\marg{theorem group}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_add_theorem_to_group:n #1
+  {
+%    \end{macrocode}
+% As mentioned earlier, this bool will indicate whether we are 
+% executing a \mymeta{selection body} from some family options.
+% If used outside, we emit an error message.
+%    \begin{macrocode}
+    \bool_if:NTF \l_@@_in_family_options_environment_bool
+      {
+        \clist_put_left:Nn \l_@@_group_clist { #1 }
+      }
+      {
+        \msg_error:nn { groupthm } { misuse ~ add ~ theorem ~ to ~ group }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\AddTheoremToGroup}
+%    \begin{syntax}
+%       \cs{AddTheoremToGroup}\marg{theorem group}
+%    \end{syntax}
+%		 
+%     
+%
+%    \begin{macrocode}
+  \NewDocumentCommand { \AddTheoremToGroup } { m }
+  {
+    \groupthm_add_theorem_to_group:n { #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}{\@@_declare_theorem_family_options_aux:nnnnn}
+%    \begin{syntax}
+%       \c{@@_declare_theorem_family_options_aux:nnnnn}\marg{theorem family}
+%        \marg{argument specification}\marg{selection body}\marg{extra groups}\marg{declaring backend}
+%    \end{syntax}
+%		 
+%     This declares a new theorem variant option parser, i.e.~ introduces the environment
+%     \mymeta{theorem family} with signature \marg{argument specification}.
+% 
+%     The \mymeta{selection body} will be executed and selects some groups the environment shall have.
+%     The \mymeta{extra groups} will be added regardless of the arguments given
+%     to the \mymeta{theorem family}
+%     The \mymeta{declaring backend} is one of \texttt{New}, \texttt{Renew}, \texttt{Provide}
+%     and \texttt{Declare} and is given to the \texttt{DocumentEnvironment} command from \pkg{xpars}.
+%
+%    \begin{macrocode}
+\cs_new:Npn \@@_declare_theorem_family_options_aux:nnnnn #1 #2 #3 #4 #5
+  {
+    \use:c{ #5 DocumentEnvironment }
+      { #1 }
+      { #2 }
+      {
+%    \end{macrocode}
+% We can now clear the group list and execute the \mymeta{selection body}
+% that populates this list again.
+% Additionally, we add the groups that should always be present and activate the
+% \cs{AddTheoremToGroup} macro by setting the bool.
+%    \begin{macrocode}
+        \clist_clear:N \l_@@_group_clist
+        \bool_set_true:N \l_@@_in_family_options_environment_bool
+        #3
+        \bool_set_false:N \l_@@_in_family_options_environment_bool
+        \clist_put_right:Nn \l_@@_group_clist { #4 }
+%    \end{macrocode}
+% We now got the list of groups parsed. We sort this and start the corresponding
+% environment that has been generated by a \cs{NewGroupedTheoremFamily} command
+% or similar.
+%    \begin{macrocode}
+        \@@_sort_theorem_group_names:
+        \cs_if_exist:cTF { __#1__groups_ \clist_use:Nn \l_@@_group_clist { _ } }
+        {
+          \begin { __#1__groups_ \clist_use:Nn \l_@@_group_clist { _ } }
+        }
+        {
+          \msg_error:nnxx { groupthm } { undefined ~ theorem ~ variant }
+            { #1 }
+            { \clist_use:Nnnn \l_@@_group_clist { ~ and ~ } {, ~} { , ~ and ~ } }
+        }
+      }
+      {
+%    \end{macrocode}
+% At the end of the environment, we have to do the same parsing again.
+%    \begin{macrocode}
+        \clist_clear:N \l_@@_group_clist
+        \bool_set_true:N \l_@@_in_family_options_environment_bool
+        #3
+        \bool_set_false:N \l_@@_in_family_options_environment_bool
+        \clist_put_right:Nn \l_@@_group_clist { #4 }
+%    \end{macrocode}
+% End the corresponding environment.
+%    \begin{macrocode}
+        \@@_sort_theorem_group_names:
+        \end { __#1__groups_ \clist_use:Nn \l_@@_group_clist { _ } }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% 
+%
+%  All other macros are now essentially wrappers around this aux macro,
+%  passing different \mymeta{extra groups} to them
+%
+% \begin{macro}{\groupthm_new_grouped_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_new_grouped_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_grouped_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { New }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\groupthm_renew_grouped_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_renew_grouped_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_renew_grouped_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { Renew }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\groupthm_provide_grouped_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_grouped_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_grouped_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { Provide }
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% 
+% 
+% \begin{macro}{\groupthm_declare_grouped_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_declare_grouped_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_declare_grouped_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { Declare }
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% 
+% 
+% The variants without \enquote{grouped} in their name will just issue two commands,
+% one with and one without the \texttt{starred} group, and add a \enquote{*} to the name.
+% 
+% \begin{macro}{\groupthm_new_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_new_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_new_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { New }
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1* } { #2 } { #3 } { starred } { New }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% \begin{macro}{\groupthm_renew_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_renew_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_renew_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { Renew }
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1* } { #2 } { #3 } { starred } { Renew }
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\groupthm_provide_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_provide_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_provide_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { Provide }
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1* } { #2 } { #3 } { starred } { Provide }
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\groupthm_declare_theorem_family_options:nnn}
+%    \begin{syntax}
+%       \cs{groupthm_declare_theorem_family_options:nnn}\marg{theorem family}
+%       \marg{signature}\marg{selection body}
+%    \end{syntax}
+%		 
+%
+%    \begin{macrocode}
+\cs_new:Npn \groupthm_declare_theorem_family_options:nnn #1 #2 #3
+{
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1 } { #2 } { #3 } { } { Declare }
+  \@@_declare_theorem_family_options_aux:nnnnn
+    { #1* } { #2 } { #3 } { starred } { Declare }
+}
+%    \end{macrocode}
+% \end{macro}
+%
+% 
+% It remains to wrap these into document commands 
+% 
+%
+% \begin{macro}{\NewGroupedTheoremFamilyOptions, \NewGroupedTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{NewGroupedTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \NewGroupedTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_new_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_new_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\RenewGroupedTheoremFamilyOptions, \RenewGroupedTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{RenewGroupedTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \RenewGroupedTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_renew_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_renew_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\ProvideGroupedTheoremFamilyOptions, \ProvideGroupedTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{ProvideGroupedTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \ProvideGroupedTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_provide_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_provide_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\DeclareGroupedTheoremFamilyOptions, \DeclareGroupedTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{DeclareGroupedTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \DeclareGroupedTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_declare_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_declare_grouped_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% 
+%
+% \begin{macro}{\NewTheoremFamilyOptions, \NewTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{NewTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \NewTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_new_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_new_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% \begin{macro}{\RenewTheoremFamilyOptions, \RenewTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{RenewTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \RenewTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_renew_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_renew_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\ProvideTheoremFamilyOptions, \ProvideTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{ProvideTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \ProvideTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_provide_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_provide_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% \begin{macro}{\DeclareTheoremFamilyOptions, \DeclareTheoremFamilyOptions*}
+%    \begin{syntax}
+%       \cs{DeclareTheoremFamilyOptions}\marg{family name}\marg{signature}
+%       \marg{selection body}
+%    \end{syntax}
+%		 
+%    \begin{macrocode}
+\NewDocumentCommand { \DeclareTheoremFamilyOptions } { s m m m }
+{
+  \IfBooleanTF { #1 }
+  {
+    \groupthm_declare_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      {
+        #4
+        \groupthm_add_theorem_to_group:n { unnumbered }
+      }
+  }
+  {
+    \groupthm_declare_theorem_family_options:nnn
+      { #2 }
+      { #3 }
+      { #4 }
+  }
+}
+%    \end{macrocode}
+% \end{macro}
+% 
+% 
+% 
+% 
+% 
+% 
+%    \begin{macrocode}
+%</package>
+%    \end{macrocode}
+%
+%   \end{implementation}
+% 
+% 
+% 
+% 
+% \ExplSyntaxOn
+% \__codedoc_special_index_module:nnnnN { key } { macro } { module } { main } { \c_false_bool}
+% \__codedoc_special_index_module:nnnnN { l } { bla } { module } { usage } { \c_false_bool}
+% \ExplSyntaxOff
+% 
+% \newpage
+% \PrintIndex
diff --git a/doc/environments/groupthm/groupthm.dtx b/doc/environments/groupthm/groupthm.dtx
index 44c10d9..958a96a 100644
--- a/doc/environments/groupthm/groupthm.dtx
+++ b/doc/environments/groupthm/groupthm.dtx
@@ -712,13 +712,13 @@
 %
 % \begin{function}
 % {
-%   \groupthm_new_theorem_group_from_keys:nn,
-%   \groupthm_renew_theorem_group_from_keys:nn,
+%   \groupthm_new_group_from_keys:nn,
+%   \groupthm_renew_group_from_keys:nn,
 %   \groupthm_provide_theorem_group_from_keys:nn,
 %   \groupthm_declare_theorem_group_from_keys:nn
 % }
 %   \begin{syntax}
-%     \cs{groupthm_new_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%     \cs{groupthm_new_group_from_keys:nn}\marg{keys}\marg{theorem group}
 %   \end{syntax}
 %
 %    \LaTeX3 versions of \cs{NewTheoremGroup}, \cs{RenewTheoremGroup},
@@ -730,23 +730,23 @@
 %
 % \begin{function}
 % {
-%   \groupthm_new_theorem_group:nnnnn,
-%   \groupthm_renew_theorem_group:nnnnn,
+%   \groupthm_new_group:nnnnn,
+%   \groupthm_renew_group:nnnnn,
 %   \groupthm_provide_theorem_group:nnnnn,
 %   \groupthm_declare_theorem_group:nnnnn,
-%   \groupthm_new_theorem_group:nVVVV,
-%   \groupthm_renew_theorem_group:nVVVV,
+%   \groupthm_new_group:nVVVV,
+%   \groupthm_renew_group:nVVVV,
 %   \groupthm_provide_theorem_group:nVVVV,
 %   \groupthm_declare_theorem_group:nVVVV
 % }
 %   \begin{syntax}
-%     \cs{groupthm_new_theorem_group:nnnnn}\marg{theorem group}\marg{prefix tl}
+%     \cs{groupthm_new_group:nnnnn}\marg{theorem group}\marg{prefix tl}
 %     \marg{suffix tl}\marg{mapname clist}\marg{thmtools clist}
 %   \end{syntax}
 %  
 % Non-keyval versions of
-% \cs{groupthm_new_theorem_group_from_keys:nn},
-% \cs{groupthm_renew_theorem_group_from_keys:nn},
+% \cs{groupthm_new_group_from_keys:nn},
+% \cs{groupthm_renew_group_from_keys:nn},
 % \cs{groupthm_provide_theorem_group_from_keys:nn}
 % and
 % \cs{groupthm_declare_theorem_group_from_keys:nn}
@@ -1501,7 +1501,7 @@
 % \texttt{new}, \texttt{renew}, \texttt{provide} and \texttt{declare} variants
 % of the theorem group macro:
 % 
-% \begin{macro}{\groupthm_new_theorem_group:nnnnn, \groupthm_new_theorem_group:nVVVV}
+% \begin{macro}{\groupthm_new_group:nnnnn, \groupthm_new_group:nVVVV}
 %		 
 %    \begin{macrocode}
 \cs_new:Npn \@@_define_aux:nnnNNNn #1 #2 #3 #4 #5 #6 #7
@@ -1544,112 +1544,64 @@
 }
 \cs_generate_variant:Nn \@@_define_aux:nnnNNNn { n n n c N N n }
 
-\cs_new:Npn \groupthm_new_theorem_group:nnnnn #1 #2 #3 #4 #5
+\cs_new:Npn \@@_define_list_aux:nnnNNnn #1 #2 #3 #4 #5 #6 #7
 {
-  \@@_define_aux:nnncNNn
-    { new }
-    { theorem group }
-    { #1 }
-    { @@_use_group_#1: }
-    \@@_undefine_group_aux:n
-    \@@_define_group_aux:nnnnn
+  \cs_set:Npn \@@_map_aux:n ##1
+  {
+    \cs_new:cn { #6 }
     {
-      { #1 } { #2 } { #3 } { #4 } { #5 }
+      \@@_define_aux:nnncNNn
+        { ##1 }
+        { #2 }
+        { ####1 }
+        { #3 }
+        #4
+        #5
+        {
+          #7
+        }
     }
+  }
+  \clist_map_function:nN { #1 } \@@_map_aux:n
 }
+
+
+\@@_define_list_aux:nnnNNnn
+  { new, renew, provide, declare }
+  { theorem group }
+  { @@_use_group_##1: }
+  \@@_undefine_group_aux:n
+  \@@_define_group_aux:nnnnn
+  { groupthm_#1_group:nnnnn }
+  { { ##1 } { ##2 } { ##3 } { ##4 } { ##5 } }
 %    \end{macrocode}
 %
 % Finally, generate some extra variant.
 %
 %    \begin{macrocode}
-\cs_generate_variant:Nn \groupthm_new_theorem_group:nnnnn { n V V V V }
-%    \end{macrocode}
-% \end{macro}
-% 
-% 
-% 
-% \begin{macro}{\groupthm_renew_theorem_group:nnnnn, \groupthm_renew_theorem_group:nVVVV}
-%		 
-%    \begin{macrocode}
-\cs_new:Npn \groupthm_renew_theorem_group:nnnnn #1 #2 #3 #4 #5
-  {
-    \cs_if_exist:cTF { @@_use_group_#1: }
-      {
-        \@@_undefine_group_aux:n { #1 }
-        \@@_define_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
-      }
-      {
-        \msg_error:nnnnn { groupthm } { wrong ~ definition }
-          { theorem ~ group } { #1 } { not }
-      }
-  }
-%    \end{macrocode}
-%
-% Finally, generate some extra variant.
-%
-%    \begin{macrocode}
-\cs_generate_variant:Nn \groupthm_renew_theorem_group:nnnnn { n V V V V }
+\cs_generate_variant:Nn \groupthm_new_group:nnnnn { n V V V V }
 %    \end{macrocode}
 % \end{macro}
 %
-%
-%
-% \begin{macro}{\groupthm_provide_theorem_group:nnnnn, \groupthm_provide_theorem_group:nVVVV}
-%
 %    \begin{macrocode}
-\cs_new:Npn \groupthm_provide_theorem_group:nnnnn #1 #2 #3 #4 #5
-  {
-    \cs_if_exist:cF { @@_use_group_#1: }
-      {
-        \@@_define_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
-      }
-  }
+
 %    \end{macrocode}
-%
-% Finally, generate some extra variant.
-%
-%    \begin{macrocode}
-\cs_generate_variant:Nn \groupthm_provide_theorem_group:nnnnn { n V V V V }
-%    \end{macrocode}
-% \end{macro}
 % 
 % 
-%
-% \begin{macro}{\groupthm_declare_theorem_group:nnnnn, \groupthm_declare_theorem_group:nVVVV}
-%		 
-%
-%    \begin{macrocode}
-\cs_new:Npn \groupthm_declare_theorem_group:nnnnn #1 #2 #3 #4 #5
-  {
-    \cs_if_exist:cT { @@_use_group_#1: }
-      {
-        \@@_undefine_group_aux:n { #1 }
-      }
-      \@@_define_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
-  }
-%    \end{macrocode}
-%
-% Finally, generate some extra variant.
-%
-%    \begin{macrocode}
-\cs_generate_variant:Nn \groupthm_declare_theorem_group:nnnnn { n V V V V }
-%    \end{macrocode}
-% \end{macro}
-% 
 % 
 % With the \cs{@@_set_normalized_keys:nnn} macro at hand,
 % it is also easy to provide key-value interfaces for these commands:
 %
-% \begin{macro}{\groupthm_new_theorem_group_from_keys:nn}
+% \begin{macro}{\groupthm_new_group_from_keys:nn}
 %    \begin{syntax}
-%       \cs{groupthm_new_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%       \cs{groupthm_new_group_from_keys:nn}\marg{keys}\marg{theorem group}
 %    \end{syntax}
 %		 
 %    \begin{macrocode}
-\cs_new:Npn \groupthm_new_theorem_group_from_keys:nn #1#2
+\cs_new:Npn \groupthm_new_group_from_keys:nn #1#2
 {
   \@@_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
-  \groupthm_new_theorem_group:nVVVV { #2 }
+  \groupthm_new_group:nVVVV { #2 }
     \l_@@_prefix_tl
     \l_@@_suffix_tl
     \l_@@_mapname_clist
@@ -1660,16 +1612,16 @@
 %
 %
 %
-% \begin{macro}{\groupthm_renew_theorem_group_from_keys:nn}
+% \begin{macro}{\groupthm_renew_group_from_keys:nn}
 %    \begin{syntax}
-%       \cs{groupthm_renew_theorem_group_from_keys:nn}\marg{keys}\marg{theorem group}
+%       \cs{groupthm_renew_group_from_keys:nn}\marg{keys}\marg{theorem group}
 %    \end{syntax}
 %		 
 %    \begin{macrocode}
-\cs_new:Npn \groupthm_renew_theorem_group_from_keys:nn #1#2
+\cs_new:Npn \groupthm_renew_group_from_keys:nn #1#2
 {
   \@@_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
-  \groupthm_renew_theorem_group:nVVVV { #2 }
+  \groupthm_renew_group:nVVVV { #2 }
     \l_@@_prefix_tl
     \l_@@_suffix_tl
     \l_@@_mapname_clist
@@ -1727,7 +1679,7 @@
 %    \begin{macrocode}
 \NewDocumentCommand{\NewTheoremGroup}{ O{} m }
   {
-    \groupthm_new_theorem_group_from_keys:nn { #1 } { #2 }
+    \groupthm_new_group_from_keys:nn { #1 } { #2 }
   }
 %    \end{macrocode}
 % \end{macro}
@@ -1739,7 +1691,7 @@
 %    \begin{macrocode}
 \NewDocumentCommand{\RenewTheoremGroup}{ O{} m }
   {
-    \groupthm_renew_theorem_group_from_keys:nn { #1 } { #2 }
+    \groupthm_renew_group_from_keys:nn { #1 } { #2 }
   }
 %    \end{macrocode}
 % \end{macro}
diff --git a/doc/environments/groupthm/groupthm.sty b/doc/environments/groupthm/groupthm.sty
index 1402d99..cade1ed 100644
--- a/doc/environments/groupthm/groupthm.sty
+++ b/doc/environments/groupthm/groupthm.sty
@@ -260,63 +260,50 @@
 }
 \cs_generate_variant:Nn \__groupthm_define_aux:nnnNNNn { n n n c N N n }
 
-\cs_new:Npn \groupthm_new_theorem_group:nnnnn #1 #2 #3 #4 #5
+\cs_new:Npn \__groupthm_define_list_aux:nnnNNnn #1 #2 #3 #4 #5 #6 #7
 {
-  \__groupthm_define_aux:nnncNNn
-    { new }
-    { theorem group }
-    { #1 }
-    { __groupthm_use_group_#1: }
-    \__groupthm_undefine_group_aux:n
-    \__groupthm_define_group_aux:nnnnn
+  \cs_set:Npn \__groupthm_map_aux:n ##1
+  {
+    \cs_new:cn { #6 }
     {
-      { #1 } { #2 } { #3 } { #4 } { #5 }
+      \__groupthm_define_aux:nnncNNn
+        { ##1 }
+        { #2 }
+        { ####1 }
+        { #3 }
+        #4
+        #5
+        {
+          #7
+        }
     }
+  }
+  \clist_map_function:nN { #1 } \__groupthm_map_aux:n
 }
-\cs_generate_variant:Nn \groupthm_new_theorem_group:nnnnn { n V V V V }
-\cs_new:Npn \groupthm_renew_theorem_group:nnnnn #1 #2 #3 #4 #5
-  {
-    \cs_if_exist:cTF { __groupthm_use_group_#1: }
-      {
-        \__groupthm_undefine_group_aux:n { #1 }
-        \__groupthm_define_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
-      }
-      {
-        \msg_error:nnnnn { groupthm } { wrong ~ definition }
-          { theorem ~ group } { #1 } { not }
-      }
-  }
-\cs_generate_variant:Nn \groupthm_renew_theorem_group:nnnnn { n V V V V }
-\cs_new:Npn \groupthm_provide_theorem_group:nnnnn #1 #2 #3 #4 #5
-  {
-    \cs_if_exist:cF { __groupthm_use_group_#1: }
-      {
-        \__groupthm_define_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
-      }
-  }
-\cs_generate_variant:Nn \groupthm_provide_theorem_group:nnnnn { n V V V V }
-\cs_new:Npn \groupthm_declare_theorem_group:nnnnn #1 #2 #3 #4 #5
-  {
-    \cs_if_exist:cT { __groupthm_use_group_#1: }
-      {
-        \__groupthm_undefine_group_aux:n { #1 }
-      }
-      \__groupthm_define_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
-  }
-\cs_generate_variant:Nn \groupthm_declare_theorem_group:nnnnn { n V V V V }
-\cs_new:Npn \groupthm_new_theorem_group_from_keys:nn #1#2
+
+\__groupthm_define_list_aux:nnnNNnn
+  { new, renew, provide, declare }
+  { theorem group }
+  { __groupthm_use_group_##1: }
+  \__groupthm_undefine_group_aux:n
+  \__groupthm_define_group_aux:nnnnn
+  { groupthm_#1_group:nnnnn }
+  { { ##1 } { ##2 } { ##3 } { ##4 } { ##5 } }
+\cs_generate_variant:Nn \groupthm_new_group:nnnnn { n V V V V }
+
+\cs_new:Npn \groupthm_new_group_from_keys:nn #1#2
 {
   \__groupthm_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
-  \groupthm_new_theorem_group:nVVVV { #2 }
+  \groupthm_new_group:nVVVV { #2 }
     \l__groupthm_prefix_tl
     \l__groupthm_suffix_tl
     \l__groupthm_mapname_clist
     \l__groupthm_thmtools_clist
 }
-\cs_new:Npn \groupthm_renew_theorem_group_from_keys:nn #1#2
+\cs_new:Npn \groupthm_renew_group_from_keys:nn #1#2
 {
   \__groupthm_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
-  \groupthm_renew_theorem_group:nVVVV { #2 }
+  \groupthm_renew_group:nVVVV { #2 }
     \l__groupthm_prefix_tl
     \l__groupthm_suffix_tl
     \l__groupthm_mapname_clist
@@ -342,11 +329,11 @@
 }
 \NewDocumentCommand{\NewTheoremGroup}{ O{} m }
   {
-    \groupthm_new_theorem_group_from_keys:nn { #1 } { #2 }
+    \groupthm_new_group_from_keys:nn { #1 } { #2 }
   }
 \NewDocumentCommand{\RenewTheoremGroup}{ O{} m }
   {
-    \groupthm_renew_theorem_group_from_keys:nn { #1 } { #2 }
+    \groupthm_renew_group_from_keys:nn { #1 } { #2 }
   }
 \NewDocumentCommand{\ProvideTheoremGroup}{ O{} m }
   {