Just a thought about what John knew!
So, re-watching early ep. (I know, I know, one day I'll stop doing that!) and the clip when YED calls JOHN WINCHESTER on knowing about Sammy and all the children like him, AND YED's plans for said children. Well, does that include Mary's (and I guess the other mother's or father's) part in "let me in the house in ten years" agreement? Just wondering, ..did John discover that piece of information, and what would be the consequences... - am I making sense?