I have been playing my family for a little bit, and I noticed that genetics in the family are passed immediately from parent to child and seem to be random. There’s no inherenting “genes” from earlier generations. And the children seem to copy exact facial features from their parents as well.
For example, my sim and Gavin Richards had a boy and girl born together. The son had a mix of both father and mothers features but the daughter looked a lot like her father.
Time passes, the children start their own families:
Daughter has a out of wedlock child, he grows up to have exact same face as his father.
Son has an out of wedlock child, he grows up to look like a light skinned version of his father, even though his mother has Asian facial features. Son later Gets married to a black woman with blue eyes and blond hair, they have a child and she has her mothers eye and hair color, face shape lips and eyes but her dads nose.
Have yet to see if the grandparents’ features are going to show up in the future.