Who is Duane Stonehorse from Dalva and what is their importance?

Fifteen-year-old, Duane Stonehorse is Dalva's lover. He is half-Sioux and looks Native American, though he has the green eyes of a Caucasian. Duane's parents are Rachel and Wesley (Dalva's father). He is a hard worker, loves horses, and leaves the reservation because he is unhappy there. When he eventually asks for permission to marry Dalva, he learns that she is his half-sister and runs away. Over the course of the novel, Duana battles alcohol and drugs. In the end, he learns he is dying and contacts Dalva, who he marries in order to provide her with his benefits. He commits suicide immediately followinng their wedding.