Originally Posted by TheComicbookKid
Superman's Red trunks
Batman's blue trunks
Characters are iconic. Traits simply help define them. Johnny's "blonde" look is a shorthand more than it's iconic. Johnny and Sue could be white and 1st cousins and that wouldn't change the family dynamic that the FF is about.
I was ok until this....
The relationship between siblings is far different than that of 1st cousins.
NOW, you want to call them 1st cousins that grew up like brother and sister, then ok. But that is still a sibling relationship, and would be a stupid change. If they grew up as sister and brother, then they might as well be sister and brother.