Branch off of the original surname Vaughn. Branching off occurred when the family originated in Wales as peasants. A few members of the original clan refused to discontinue beastiality and were exciled and forced to take the surname given to them, "Vaughan" with an added "A" to represent their afflication for animal (interspecies) erotica.
Roxy: Dude, I love Vince Vaughan!
Bobby: It's spelled V-a-u-g-h-n, he's not decended from the banished clan members.