Ideas
Hi everyone! I figured out something and how to fix it, at least for me.
So my info: 2 female sims. One was originally an NPC (Alice who was resurrected and then manually added to family via cheats). 1 science baby between them, 2 children with Grim, one with each parent. I used MCCC mod to make the two grim children both of their children instead of just dependents of the other spouse. I'm not certain what here messed this up, because I had no problems UNTIL:
Using a cheat to open full CAS.
Opening full CAS in my case for some reason made the game recognize the spouses as sisters, and even after using MCCC to manually set relationships afterward, it would still cause the issue as soon as CAS was opened in any form.
I'm not entirely sure what triggers the issue, or if the above issue even has anything to do with the manually added family ties, but to fix it, I removed all family ties from each child between their parents and each other using MCCC, as well as between the spouses, then I edited the family in full CAS and assigned their roles as spouses/parents/siblings.
Everything is working fine now, and interestingly, in addition, an issue I was having with Alice where her eyes were white has resolved now and she now has brown eyes. Grim does not appear to be a parent anymore, but I'm not certain how to actually check.
Not sure what here is relevant to the issue. I'm curious to see if my case shares anything in common with others.