Superman Jr. of Earth-E
From superman.nu: Supermanica
Superman Jr., who's secret identity is Clark Kent Jr. of Earth-E, is the super-son of the Superman of Earth-E. On Earth-1 however, he is nothing more than a character in a computer program. Just as Superman formed the world's finest team with Batman, so too did Superman Jr. team up with Batman's son, Batman Jr. of Earth-E to form the team of the Super-Sons.
(WF No. 215, Jan 1972: "Saga of the Super-Sons!")