Mary Marvel is a fictional character, a comic book superheroine, originally published by Fawcett Comics and now owned by DC Comics. Created by Otto Binder and Marc Swayze, she first appeared in Captain Marvel Adventures #18 (cover-dated Dec. 1942). The character is a member of the Marvel/Shazam Family of heroes associated with the superhero Shazam/Captain Marvel.She is the alter ego of teenager Mary Batson (adopted name Mary Bromfield), twin sister of Captain Marvel's alter-ego, Billy Batson.