Cyrus Mitchell was the human son of the vampire Tom Mitchell.
Cyrus' mother had died of an unknown illness, and his father Tom died in 1922, when he was killed and sired by a vampire. Tom still came to visit him, and took him out some nights to the Santa Monica Pier.
Cyrus left to join the war in 1945, and after he returned he married a woman named Marcie, with whom he had a child in 1950. Marcie's mother didn't want Tom around the baby, which Cyrus had to tell him. Tom killed Cyrus' mother-in-law, after which Cyrus raised his family without seeing his father for 50 years.
In 2000 Cyrus, now an old man, contacted his father because he knew he didn't have much time left. Three years later, the door of the place Cyrus and his father were staying was kicked in by a Slayer, who staked Tom.