How exactly does Christy + Baxter = Roscoe?

First, let me make it clear, this is not about race. It is about genetics. Am I wrong in observing that the kid who plays Roscoe is either Hispanic or just dark complected? Either way, blond paleface Christy had a baby with brown-haired paleface Baxter. And the baby was a dark haired, dark complected Roscoe? Is Hollywood running that low on child actors? 'Coz the world ain't runnin' low on children.