When the skin tone update first came out, I tested it in CAS, I had the dad in the warm tones, and the mom in the cool tones, originally for both. Father was extremely pale with blonde hair and blue eyes, with the mother being dark skinned with black hair and brown eyes. Before moving the mom into the same warm color slot as her husband, I got some weird skin tones that the parents wouldn't actually have, even with the darkest or lightest version of both of their tones. Some skin tones were a grayish color.
When I moved both parents into the warm tones category, the kids ended up getting less drastic skin tones, and actually looked like they could be a mixture of their parents.
Also, hair and eyes can be a bit weird as well when it comes to family as well. I have had parents with blues eyes, and green eyes, in the first generation, and their kid comes out with a gray, which doesn't match their parents. I can kind of see if they had a parent with occult eyes, since that is a problem with the genetics in the game, but when both eyes are normal, and the kid doesn't inherit either one, can be kind of strange. Especially, being from two parents in the first generation.
Also, back to the hair, and a bit on the eyes, some genetics aren't really passed on realistically. In previous versions, like Sims 2, if a parent with blonde hair and blue eyes were married to a sim with Black hair and brown eyes, the kids would mostly inherit the dominant genes, like the brown eyes and hair. In the Sims 4, If I have a blonde haired blue eyed sim married to a black haired brown eyed sim, I have had cases where most of the kids are blonde. Which isn't terrible, but I feel that the majority should be black. Weirdly, though, I have had a blonde married to a redhead, and only one of their kids was a blonde, the rest were redheads.
So yeah, Sims 4 does need to be fixed a bit, because if the parents of a Sim are in different skin tone categories the result is weird skin tones that aren't even close to the parents. Eyes don't match to either parent, especially the first generation, where they shouldn't have that issue. Also, with blonde versus black hair, I shouldn't have so many blondes with genetics.
