Schlossberg was born in New York City on January 19, 1993, to museum exhibit designer Edwin Schlossberg and Caroline Kennedy, daughter of U.S. president John F. Kennedy and First Lady Jacqueline Bouvier Kennedy. He was named after his maternal great-grandfather, John Vernou Bouvier III. Schlossberg has two older sisters, Rose and Tatiana. Schlossberg's father comes from an Orthodox Jewish family of Ukrainian descent, and his mother is a Catholic of Irish, French, Scottish, and English descent. Schlossberg was raised in his mother's religion, and he also observes Jewish traditions, holidays, and holy days. As the lone grandson of John and Jacqueline Kennedy, Schlossberg became the only surviving male descendant of JFK's immediate family after his maternal uncle, John F. Kennedy Jr., died in a plane crash in 1999.