Húrin is supposed to be the shorter of the brothers, I think? (- That's why I suggested DiCaprio, who's not as tall). I think he could play Huor though, who's supposed to be the tallest except for Tuor.I agree that we should find a role for Chris Hemsworth. He's not usually as bulky as he is when he plays Thor; he's trimmer in his other roles. Maybe Húrin?
A 6'3" pretty red-headed guy with a bit of a dark side for Maedhros the Tall sounds perfect; I haven't seen Outlander, but we should probably at least consider this guy for the role.