Child to archaeologists C.C. and Marylin Batson, Billy Batson's parents were killed by their assistant, Theo Adam, while on a dig at the tomb of Rameses II at Abu Simbel, Egypt. Separated from his sister and left in the care of his uncle, who later stole his trust fund money and threw him out, Billy eked out an existence in Fawcett City as a newsboy while sleeping in subway terminals.
Guided to the Rock of Eternity, Billy was chosen by the wizard Shazam to become the new champion of mankind; bestowing extraordinary power by speaking the wizard's name; transforming the boy into the adult Shazam, a hero possessing the wisdom of Solomon, the strength of Hercules, the stamina of Atlas, the power of Zeus, the courage of Achilles, and the speed of Mercury (S.H.A.Z.A.M.).
Although looking like an adult as Shazam, Billy is actually not much older than Robin.
In keeping with then-comic-book-canon; Shazam was originally named "Captain Marvel" in DC Universe Online, however, in mid-2012 DC Comics requested that DC Universe Online change his name to Shazam in order to keep the character up to date with his comic book reboot. As such, in his The Last Laugh T3 Duo appearance he is named Shazam, however, in all other in-game appearances he is still named "Captain Marvel".
Captain Marvels name was changed to Shazam due to copy rights from the super hero franchise MARVEL.