Mary Tsepesh (neé Windham) was the wife of Arkady Tsepesh. When she was pregnant in 1845, they were called into the service of Arkady's "Uncle" Vlad. When she had Arkady's baby, Stefan Tsepesh II, she had to run from Dracula so he wouldn't enslave their child. To get Dracula away from Stefan she shot Arkady with a pistol, and Dracula turned him into a vampire to prevent him from dying.
Mary, mistaking her husband for dead, left to England and married Jan Van Helsing, and they adopted Abraham Van Helsing.