I think this same sort of pattern works with all the people-oriented games from LDW. I know for a fact that people track their VF families with the bigheads image in the picture files for VF. (that one shows all of the heads for both genders)
The principle is the same, the heads in between the two heads of the parents are the mostly likely ones the children will have. (of course, there are a few rare kids that don't follow that line)