All recent prospects bar Mills and Jawai (any others?) have significant roots elsewhere (considering only the last few thousand years, let's say). Not like Newley, Ingles, etc have had families here for more than several generations.
But yes, I think that having a basketballer parent has probably given Exum, Simmons, Bolden, etc a handy start. These kids would've been handling a basketball and hanging around courts from a young age.
Genetics would play a part to some extent, but height is probably key too.
DMac has a kid who got somewhere, but without the forecast these three have. Cecil, Dave and Bruce were all pretty tall and coupling tall kids with early skill development wouldn't hurt. Lindsay Gaze's son is about as white as they come, but has height on his side.
As for Maker, I think height is a huge part of his appeal. Sudanese average height is pretty tall.