How many kids do you prefer to have per couple?

I'm obsessed with genetics, but lately having lots of kids has been hard to play, so I've made a rule for my families: Make them patriarchal or matriarchal, and keep making them have kids until they have a child from both of them that's the correct gender. For every time the guy fails to get the girl pregnant, she can have an affair (with or without protection), and the guy can have an affair every time she has a child of the wrong gender (with or without protection). ^_^ It means my sims have 2 kids on average, but some families only have 1, and some end up with 8!