Milo is one of Lyra's school friends and one of the main characters in books 2-3
Milo Peterson (pronouned My-low) had a school-boy crush and infatuation with Lyra all the way through school. He knew about the existance of the supernatural, but was so loyal to Lyra that he never told anybody what he discovered. He was always a very smart person, so naturally, when Lyra, Maranda, Laney, and Hannah, went to Italy, he went to college. While studying there, he discovered a secret about the Seely Court, and told Lyra imediatly. He still stays very loyal to Lyra, even though she is married.