He thinks keeping magic from muggles is a selfish thing to do. He dislikes the Ministry of Magic because of his mother imprisoned in Azkaban for performing magic in front of muggles. His father and brother are muggles and in prison too. At first he can come off as a solitary, studious boy who prefers focusing on his academics over interacting with others, but he really hopes to have some good friends to become more open and sociable. He's the best in potions and will never betray his friends.