In Superman #65 (May 1950), “Three Supermen from Krypton!” establishes for the first time that Superman is not the last surviving Kryptonian. Three brothers U-ban, Kizo, and Mala, arrive on Earth with Superman’s powers and wreak havoc. Superman discovers they are also survivors of Krypton who were members of the “Ruling Council” that had attempted to take control of Krypton but were defeated by Jor-el and imprisoned in a “unique plastic shell” and then shot off into space.
Superman challenges the trio to a duel on a deserted island where no Earthlings can be hurt.
The writers made the mistake of making invulnerability to the extreme, which makes me wonder how Superman is so exhausted later:
Superman uses ventriloquism to bait the three brothers into fighting each other all night so that the next morning, Superman is easily able to overcome them. Imprisoning them in the same vessel that his father did years earlier, he sends them back out into space.
The overall premise is almost the exact same as the film Superman II with U-ban replaced by General Zod. I’m surprised these three Kryptonians are not more prominent in the Superman mythos!
Known surviving Kryptonians: 4.
P.S. Kryptonians are called “kryptonites” in this issue.