I Did Not sign up for This (Birds and Bees)
Being stuck with two teenagers was not what Bobby Singer was expecting; though, he was taking care of them most of the time as children. Some part of him though that it would settle down once they matured but unfortunately, for all parties involved, that wasn't the case. So, because most of the time their schooling wasn't the best - and the holes in said schooling was glaringly obvious and disheartening at times - Bobby sometimes took it upon himself to teach them basic things.
But sexual education wasn't exactly basic and he had never expected to have that burden pushed on him. But since Sam and Dean were getting to be that age, he figured that he might as well tell them what they needed to know, and maybe some hints for when they got that far along.
For the most part, Dean had been taught - both by Bobby and by school - a fair amount of sex ed. Sam on the other hand, even though he was a bit bookish, seemed to be lacking in that regard. And that was one avenue that Bobby wasn't raring to go down with the younger boy.
Maybe Sam knew what to expect when he walked into the kitchen and saw the books on the table and Bobby's expression. "Did they ever teach you about sex in school?" Perhaps not his best opening line, but it was better to take the blunt approach with these boys.
God, this was going to be rough.