He was the result of a eugenics experiment in 20th century England, attempting to create super-soldiers in case of German invasion. However, Mary decided she no longer wanted to be involved in the project. She faked the miscarriage of Ray, then divorced Kinsella. He did not know of Ray's existence until years later.
When he grew up, Ray became psychotic like the other children of the project. He tried to free the ones held by the Wilcock Institute. However, Templeton gassed the building to stop him. This enraged Ray, and Kinsella was forced to kill his own son. (AUDIO: Sins of the Fathers)