Married couple suddenly becomes sisters…

So i play on Playstation 5. 
My two female sims were together for about two weeks and got happily married. Then after some time they got a daughter together through sciencebaby option. Suddenly after she was born none of them could do any romantic interactions with eachother. Upon looking at relationships gave me a huge shock. They were suddenly sisters…..

I tried moving them out seperatly and divorcing them. Nothing helps to remove it. I have never used cheats and never will either. This is a obvious very serious bug/glitch that is completely ruining my game. Any help on What to do would be appriciated.