Born October 16, 1926, in Saugerties, New York, Joe Sinnott was one of seven children to Edward and Catherine McGraw Sinnott; his siblings were Edward and five who predeceased him: Ann / Anne, Frank, John a.k.a. Jack, Leonard and Richard. He grew up in a boarding house that catered primarily to schoolteachers, some of whom inspired in the young Sinnott a love of drawing. His childhood comics influences include the comic strip "Terry and the Pirates" and the comic book characters Batman, Congo Bill, Hawkman and Zatara. Sinnott attended the schools St. Mary of the Snow and Saugerties High School.