Born to Jorel and Lara in the science capital on Vathlo Island on Krypton, baby Kalel was sent to Earth to escape his homeworld's destruction. He was found and raised by a human couple. As an adult, he operates as Superman while also serving as the President of the United States on Earth-23.
Calvin Ellis made his debut in Final Crisis #7, being that his only appearance before the Flashpoint reboot. Beyond being revealed than Nubia and him were from the same Earth and his job, little was known about him.
Major Story Arcs
The Curse of Superman
One day, inhabitants from an alternate Earth (scientists Clark Kent, James Olsen and Lois Lane) came through a transmatter symphonic array to his Earth, running away from Superdoom, their universe's Superman who already had killed others Superman doppelgangers. When the evil Superman came through, Superman fought him and won, with the help of his archenemy Lex Luthor.
In Multiversity it was revealed than Superman (Calvin Ellis) is member of his own world's Justice League composed mostly by afro-american heroes. When Thunderer called for help through the 52 universes, Calvin was the last summoned. However, he was ready to help to rescue the last Monitor and stop the menace of the Gentry, depiste the resistance of the Retaliators of earth-8.
However, Superman discovered than Nix Uotan had been corrupted by the Gentry and he was attacking earth-8. With the help of heroes of several parallel earths, the menace of the Gentry was stopped, but not before discovering from where were all those problems being originated: earth-33.
Worried about the potential threats than could menace the multiverse as a whole, Superman asked for volunteers to put in effect a multiversal task force to defend all the universes in case of another attack: Operation Justice Incarnate had born. For President Superman, it's just another job on top of his Presidency and work as Superman.