Reubens was born Paul Rubenfeld in Peekskill, New York, and grew up in Sarasota, Florida, where his parents, Judy (Rosen) and Milton Rubenfeld, owned a lamp store. His mother was a teacher. His father was an automobile salesperson who had flown for Britain's Royal Air Force and for the U.S. Army Air Forces in World War II, and later became one of the founding pilots of the Israeli Air Force during the 1948 Arab–Israeli War. Reubens' two younger siblings are Luke (born 1958), who is a dog trainer, and Abby (born 1953), who is an attorney and a board member of the American Civil Liberties Union of Tennessee.