Dean loses his virginity at the age of fifteen, to a girl three years older than him, in the back of the impala in a state he can't even remember the name of.
He doesn't love her.
He's only just met her a few hours before at some crappy party, and it's messy and unromantic and Dean lasts approximately three and a half minutes.
Afterwards, the girl leaves pretty quickly and Dean's left laying on the cold seats of the car he's grown up in, the only home he's ever had, feeling like a man and a little boy all at once.
Castiel loses his virginity when he's been human for two and a half months, and alive for longer than any other human can possibly comprehend. He loses his virginity in the arms of the only man he's ever loved, and the man he's sure he'll love for the rest of his life. With Dean pressed up close to his chest, Dean's breath hot on his cheeks, and Dean's legs wrapped tight around him, he wishes he could bottle the moment and keep it forever.
Afterwards, as they lay wrapped up together in their room in the bunker, Cas feels like he's finally found somewhere to call home.
Sometimes home isn't a place.