Amber - well, quite often if you look at the "lead" member of the family, they will have a blue blob - not every time, I admit, but a good percentage. Not always the father - I expect it depends on which family member the alterer (?!?) was interested in or made the original alteration on.
(is there a correct noun for the "person who made the alteration" ? Alterer is logical but it certainly doesn't look right! )