Jason's father, Arthur Robert White, was a porter at Billingsgate Fish Market, and his Welsh mother, Olwen Jones, was from Merthyr Tydfil, Glamorgan (now Merthyr Tydfil County Borough), Wales and worked as a charwoman. She gave birth to twin boys at North Middlesex Hospital in Edmonton, London, in February 1940, but Jason's twin brother died during childbirth, making him a twinless twin. He chose the stage name Jason because he liked "Jason and the Argonauts", as the stage name "David White" was already taken, and not in tribute to his dead twin as has sometimes been claimed.