John Winchester (Jeffrey Dean Morgan) is the father of Dean (Jensen Ackles) ?and Sam Winchester (Jared Padalecki). Together they make up a family of demon hunters. John entered this life when his wife Mary (Samantha Smith) was murdered by a yellow-eyed demon named Azazel (Frederic Lehne). Several years after Mary's death, John also fathers a son, Adam (Jake Abel), with nurse Kate Milligan (Dedee Pfeiffer).
Due to his desire to take revenge upon the demon that killed his wife, John became a hunter of the supernatural and trained Dean and Sam to become hunters as well. Adam did not learn about the supernatural life his father led until much later. The relationship that John had with his sons was strained due to the way they were raised. At the beginning of the show, Sam is away at college and John has disappeared. Dean reaches out to Sam for help in locating their missing father.
Eventually the entire family teams up again to defeat the yellow-eyed demon, with John having to make a deal with the demon to save Dean's life. A deal that involved his death and his soul.
"Any more questions? All right, let's get outta here, we're losin' daylight. Hey and Dean, why don't you touch up your car before you get rust. I wouldn't have given you the damn thing if I thought you were gonna ruin it. "
"You gotta understand somethin'. After your mother passed, all I saw was evil. Everywhere. And all I cared about was, was keepin' you boys alive. I wanted you prepared. Ready. So somewhere along the line I uh, I stopped being your father, and I, I became your, your drill-sergeant."