Next Time We'll Go to the Met
It’s not like Sam doesn’t know. He’s known for a long time, ever since he found what he thought was Dean’s porn stash and it turned out to be a collection of Ballet for Beginners instructional videos. Dean occasionally gets turned on by unusual stuff, but the simple videos are nothing except a muscular middle-aged woman in an empty dance studio teaching very basic ballet steps, so it’s unlikely jerkoff material even for Dean. From there, pieces started coming together. It didn’t take Sam long to figure it out.
So, yeah, Sam’s known for a while. The reason he hasn’t said anything is that he’s exercising tact. Even at the best of times, Dean has very delicate self-esteem, plus defense mechanisms that make nuclear missiles look like popguns; frankly, the situation is an absolute minefield. Sam is confident, though. He’s navigated his share of minefields over the years. He has a plan.