Thread:Artful Dodger/@comment-24751588-20131013163757/@comment-217293-20131021200420

Based on their origin story, Miss Marvel died in childbirth and Bova Ayrshire (Earth-616) convinced the Whizzer that the twins were the result of her efforrs. He couldn't handle the situation and run away, abandoning them.

They had their reunion when the twins were already in adulthood. No idea if there were any legal papers supporting the relation. Frank died in Vision and the Scarlet Witch Vol 1, still believing himself to be their father, and Magneto turned up to replace him two issues later.