They REALLY need to add a step-parent relationship...

So I know they show up in the family tree. But ingame your stepparent is just a roommate living in the same house as you. There is no special relationship flag. And when the kids Age up they can date marry or hook up with said step parent.

Now I know I will get the "you can do that in real life". Comments. But come on this is just sad and creepy.