toll no bell for me father

Dean finding out that Sam's also attracted to him and wondering - and he hates that it's his first thought too - if that means he had something that would have Sam not leave.

(answers are yes and no, respectively)

So in terms of that subject specifically, the draft of a timeline would be:

1x14 ending with Sam being curious about what the hell Dean was talking about.

Then they meet John and he starts watching Dean and John and it's like seeing them with new eyes - certainly, he has to be wrong.

(Samdean feelings are also in the background (or in the foreground too, those can never be contained), of course, which makes everything both better and worse.)

He's in denial, but Azazel then bursts the bubble and for the first time Sam truly sees his family in all its ugly truths.

2x01 goes as it does, but with Sam feeling some satisfaction for being the one who ultimately handed John the instruments of his own destruction, once he understands why John summoned the demon.

Sam does some reading on the subject and feels so guilty for never noticing what was going on, because there are so many obvious signs that Dean's displayed since forever.