I think the gender is random. I haven't noticed that there's a big drop in how many babies they have in each generation.I have a 3rd generation family on the go and they've all had 6 kids. I HAVE noticed though that in some of my games I'm encouraging less babies if the mom seems to have a high paying job. I've started alternating one family to be baby making machines and the next to have a few to carry on but mostly using them to save up money. (I hope that makes sense) I'm having fun experimenting though. I haven't had any triplets yet. The most multiples I've come across is my family that had 2 sets of twins. ALL girls and then the next generation had 6 kids, 5 of them girls, hehe.