Editing Pre-Existing Relationships Doesn't Work

I have an issue in my game. Shortly one of my active female household members gave birth to her child she was culled from my game. I luckily had the mother saved in my Library in the Gallery, so I brought her back in my game. I reunited mother and daughter in one household to bring back their relationship from before. However, there my problems started. I have full cas edit cheat enabled and I can edit everything, but not their relationship. I can even change the household relationship between the teen girl, her siblings and her father, but can't do anything between her mother and all the not culled sims. It doesn't matter whether I edit the household via the World menu or via the shift button + edit in CAS menu on one of the sims in the household after loading the family.

Whether I do it via creating the mother as her own, new household and than adding her to the one with her daughter or adding her from my Library to the existing family: in both instances the relationship is roommate and is it unclickable. Additional problem is that they are part of an already larger multi generation family with extended links across my save game, so I can't just easily save all family members in the Library and make them a new family. Also, because the parents are not married, just romantically involved. Both mother and daughter are different generations, so that should not be a problem either.

I have also restarted the game, but that didn't help, and the work around with the Sims ID's and adding their relationship via the cheat bar (relationship.add_bit yoursimID targetsimID relationshipbit) has never worked for me: that is not any different now.

EDIT: added a screenshot. It is in Dutch, but the first 3 ''huishoudlid'' (roommate) are blacked out in terms of editing, while the bottom left and the two on the right are editable, while all 6 are pre-existing members of the household and the example sim is not. All 7 have at least a limitation one way or another.