Ever since Life and Death released, when sims have a baby, it's just a male or female clone of the mom (sometimes the dad, but usually the mom) or the parent that birthed them. This happens in CAS to...
Ideas
I've seen this happen recently in my game too. I had Lilith Vatore have a baby with Rory from the werewolf pack and their daughter just looks like a clone of Lilith. No resemblance to Rory at all.