Wikipedia
The Super-Sons were a pair of fictional characters in an alternate version of the DC Comics universe. The characters were created by Bob Haney and Dick Dillin (based upon Superman by Jerry Siegel & Joe Shuster, and Batman by Bob Kane & Bill Finger). The duo first appeared in World's Finest Comics #215 (January 1973). They were based on imaginary tales about the sons of Superman and Batman with Superman's dark-haired wife and Batman's red-haired wife. Batman's imaginary son was seen first in Batman #131 (April 1960), Batman #145 (February 1962), and Batman #163 (May 1964). The Super-Sons first appeared together in World's Finest Comics Vol 1 #154 (December 1965). They later inspired the characters Joel Kent and Bruce Wayne Jr. in Superman & Batman: Generations I (January - March 1999).
The Super-Sons, Superman Jr. (Clark Kent Jr.) and Batman Jr. (Bruce Wayne Jr.), were college-aged versions of their superhero fathers. Their mothers are never fully shown (their faces either being hidden or turned away from the reader), and are never referred to by name. The Super-Sons look almost exactly like their fathers and wear identical costumes. The characters spoke with a slightly exaggerated version of the slang popular in the late 1960s and early 1970s. They regard each other as brothers, since both understand the pressures involved in being the son of a living legend. Like his father, Batman Jr. has no superhuman powers and relies on athletic prowess and gadgets. Superman Jr., only half-Kryptonian, has powers levels of only half that of Superman, Sr.
Although the very first Super-Sons appearance stated that these were actual stories in the lives of Superman and Batman, the final story in World's Finest #263, "Final Secret of the Super-Sons", written by Dennis O'Neil, revealed that the Sons had never really existed — they were merely computer simulations of what might have been, created by Superman and Batman on the Man of Steel's computer in his Fortress of Solitude.