One of the movie’s new cast members is Milo Ventimiglia, of Heroes fame, who will star alongside Twilight’s Taylor Lautner.
Ventimiglia revealed his and Lautner’s role to MTV, saying, “I'm [working] with Taylor Lautner. We're playing fraternity brothers. I haven't started [shooting] - I'm heading out the day after tomorrow - but I met him. He's a sweet kid. A very, very nice guy."
That´s the reason of his blond hair too :D
Source