Who is Harry Goldfarb from Requiem for a Dream: A Novel and what is their importance?

Harry Goldfarb is the main character. He is the son of Sara Goldfarb and Seymour Goldfarb (deceased). The novel opens with Harry as a user, stealing from his mother for drugs and ends with him completely strung out. Harry lived with his mother in Bronx for most of his life. At some point he gets caught up using heroine and his mother can't get through to him to let it go. He loved Sara but gets frustrated with the fact that her life has never changed-even though he is the one hiding from life.