The extended family

Was Heather (and the other two girls who only really appear at the start looking for shampoo etc, plus maybe the boy with glasses) daughter of the couple living in Paris? And was that Peter and Frank's other brother?

Frank and Lesley seemed a lot older, but apparently had the youngest kids - it was all a bit confusing.

EDIT: Wikipedia lists the cast out and where in the family they belong. It puts all but Heather and Kevin's brothers and sisters and the kids of Frank and Lesley (sure one of the other girls said none of her parents were around), plus male cousins named Steffan and Rod?? One of these was the one around Buzz's age seen early on, Fuller was the young one, so who was the third guy?