Harry Potter and the Half-Blood Prince
by J.K. Rowling
Voldemort's uncle (his mother's brother), Morfin is a seedy, malicious man who takes after his father. After hexing Tom Riddle, Sr. (the Gaunts hate Muggles), he is sentenced to three years in Azkaban Prison. Much later, Tom Riddle, Jr. frames him with the murder of Tom Riddle, Sr. and Tom's parents. Morfin spends the rest of his life in jail, and Dumbledore gathers a memory from him of Voldemort before Morfin dies.