There are seven official subsidiary organizations within the CDU/CSU:
Women's Union (FU; 155,000 members)
Young Union (JU; CDU/CSU's joint youth organization; 110,000 members; very powerful)
Seniors' Union (SU; 54,000 members)
Middle-Class and Trade Association (MIT; 30,000 members; very powerful)
Christian Democratic Employees' Association (CDA; many members)
East and Middle German Association (OMV)
Local-politics Association (KPV)
The Women's Union is the only sub-organization that has already committed itself. Guess to whom.
AKK also got the endorsement of the CDU Saarland state sub-organizations JU, FU, CDA and MIT.
The Seniors' Union is reported to endorse AKK, too.
There are some smaller CDU associations like the archconservative such as the "Values Union" or the "Berlin Circle" and the neoliberal Economic Advisory Council, all of which support Merz's candidacy.
Source.