Here's a thought, just pretend all the children are from different families...it's all made up and just a game after all ( what?! hehe)

Having a family tree within the game is one way to play it, I've done it a few times and it's fun to see how families turn out in the end.

BUT you have to remember, there are no actual genes involved, so I wouldn't worry so much about the inbreeding thing at the start. A perfectly normal little villager will pop out Every time no matter who breeds with whom.

Just take it as read that the first baby born is in a family, and the rest of the children are just part of the tribe and can breed with whoever they choose when they turn 18.