Flintheart Glomgold, John D. Rockerduck and Scrooge McDuck as kids. Rockerduck is a baby, because he’s supposed to be younger than the other two, who are the same age. 

Flinty and Scrooge are both born into poor families, while Rockerduck inherits his fortune.

I borrowed Scrooge’s design from Rosa, while the other two are mine.