Harry Potter and the Half-Blood Prince
Marvolo Gaunt is Voldemort's grandfather and a mean old man. He prides himself on being a pureblood wizard, particularly his Slytherin connection. He can even speak Parseltongue. He lives in a run-down shack in Little Hangleton with his son Morfin and his daughter Merope. He wears a family ring, an heirloom, which Voldemort later steals and turns into a Horcrux. Marvolo has violent tendencies and is taken to Azkaban Prison for having assaulted Bob Ogden, a Ministry official. When he is released, he finds that his daughter has abandoned him for a Muggle, and he dies, unable to care for himself.