Sampson is the son of Ralph Jr. and Aleize Sampson, and has three siblings: one older sister, Rachel, a younger brother, Robert, and a younger sister, Anna. His father was the number one overall pick in the 1983 NBA draft and played nine seasons in the NBA, earning NBA All-Star honors three times and Rookie of the Year honors in 1984. He would also be named a member of the Basketball Hall of Fame for his overall success in the sport.