Problems setting relationships in CAS

I'm having the relationship problem also. I had a baby child she aged up to a child then all of a sudden she's my sister, but the father is still her father.. I tried to use create a Sim to edit the relationship, but for some reason it will not let meme with mom and daughter, even if I do the cas cheat. But it will let me edit relationships within the father. Its really irritating.. I haven't played the Sims since the issue.