OK I get confused. Cousins is one type of peripheral line for sure, but
isn't there other peripheral lines? How about the parents of your uncle?
How about the brothers and sisters of your aunt? I also consider my wife's
family to be related to me so those are also peripheral lines. I understand
that descendants of your ancestors AKA your cousins are peripheral lines. As
far as other relatives I have never seen a specific definition of a relative
that is NOT considered a peripheral line. Perhaps ex spouses or grandparents of
your step kids?