Told to me by
yoshiinjapan, who is, as ever, a font of information.
taken from the
SPN wikipedia article
A prequel comic book,
Supernatural: Origins, detailing the early lives of John, Sam, and Dean and how they became hunters, will be published by
Wildstorm, a company under the
DC Comics company. It will begin publication in May 2007.
I'm almost very? afraid this will dash some of my own mental "canon".