Billy had been created to act as a child for Sasha and Davydd. Though Davydd tolerated Billy, Sasha hated him, believing him unnatural. When Gwen Cooper, Rhys Williams and Anwen Williams came to Rawbone in 2011, their child reminded Sasha even more of her inability to have a child. She tried to kill Billy by boiling him in the bath, but Gwen saved him.
After Sebastian took control of the Scions, he made Billy kill his own mother in the same way. Billy also attacked the rest of the town, driving out his father. After Sebastian was defeated, Tom and Josh adopted him. (PROSE: First Born)