[Robert Griffin III] doesn't look black, he is black.

I from what I have read he grew up a military brat, both of his parents being sergeants, there's little doubt that they are both black.

No doubt he was taught discipline as a child and being that his parents were lifers chances are that the child was never allowed to embrace the gangster/Ebonics culture, hence his proper use of English. But make no mistake about it, if the chips were down he could easy become a "brother" real quick.