Does it matter to you? The only argument I've heard that has any value is the fact that his sister is white. That said, mixed-race families can have children of different colours. Maybe one parent got divorced after having a child with their first spouse and had the second with their second spouse. Maybe one is adopted. He was cast for his acting abilities, not his skin colour. Also, Jessica Alba isn't exactly white yet no one freaked out about her being cast as Invisible Girl.