Jack Sheldon was the son of Jen Loven (1909-1989), who taught many of the Hollywood entertainment elite and their children to swim at her famous Jen Loven Swim School in Hollywood. Jack was known mostly for his sidekick status on the The Merv Griffin Show (1962) in the 1970s.

He had two sons, Kevin and John, and two daughters, Julie and Jesse Sheldon. John, a musician, plays drums, and attended military college prep school at the prestigious Army & Navy Academy in Carlsbad, California. He acted with his father in the Disney comedy Freaky Friday (1976), as one of the trouble-making kids who loved to harass Jodie Foster. He played in jazz clubs, most often at the Catalina Bar & Grill in Hollywood, sometimes joined by George Segal.