Who is Four?

Tobias "Four" Eaton is the initiation instructor for Dauntless transfer initiates. Four serves as Tris' instructor, as well as her love interest. Tobias was given the name "Four" because he has four fears. He was born into the Abnegation faction but chose Dauntless in order to escape the abuse of his father. When we first meet Four, he is elusive and mysterious. He is described as very protective of those he cares about.