Disclaimer: I do not own Supernatural.
Dean loved his brother. He did. And he always had, and would, no matter what.
The sad thing was how long it took him to figure out exactly how much he loved his brother.
One would think that Dean's reaction to Sam's death would have put up a red flag that perhaps, maybe, Dean loved Sam a little too much. Selling one's soul is above and beyond the call of duty for an older brother, but Dean had just been too desperate, too broken, and too frantic, to realize that perhaps, maybe, he wasn't acting by the standard definition of normal.
Had that failed, the next logical assumption would be that Dean had realized his extracurricular feelings when the Hellhounds came for him. Or, maybe, if he was slow, that he would definitely have figured it out when he actually went to Hell and screamed for no one but Sam for the equivalent of forty years. Not his mother, not his father, not any of his hundreds of girlfriends and one night stands, not Bobby, not Jo or Ellen. Sam. Always Sam.
But no. Dean was just thick enough to be able to be completely oblivious beyond even that point. He came back from the dead, as usual, and found Sam, hugged him too close for too long, and perhaps, maybe, he started to wonder about it at that point, but if he did, he ignored it.
Had Dean been a little more introspective, a little less emotionally constipated, he might have realized that he had always loved his baby brother when they were torn apart, fighting bitterly, trust gone, because of Sam's choices and the Apocalypse. When he had to chain his detoxing brother to a sink and leave him there, or when Sam went off and fucked Ruby. And if not that, surely he would have figured it all out when Sam threw himself and Lucifer into Hell. After Sam saw Dean and the car and all the memories of them, and when that was enough to give him temporary control over the Devil himself... when Dean figured out that Sam loved him that much, that way, and when it didn't bother him, maybe he should have figured out that he loved Sam that much, that way, too. That should have been enough.
But it wasn't, because Dean was a little slow at times, especially when it came to things like feelings. And love. Especially love.
Because while he had known that he loved Sam, cared about Sam more than anyone or anything, wanted to protect Sam, went crazy when he wasn't around Sam, the first moment when it occurred to Dean that he was in love with Sam was when Sam came back without his soul. When, for the first time, he wasn't Sam.
Even on demon blood, Sam had been Sam. Confused, sure, misguided, certainly, but he was still Sam. Had that overwhelming, all-consuming compassion, stubbornness, empathy. Always cared about Dean. He screwed up, but he thought he was doing the right thing. And that was very much 'Sam.'
Without his soul, though, when Dean could see the horrible contrast between his compassionate, stubborn, empathetic Sam, and this creature that happily threw him to the vampires, it was like a blinding light. Like the story of Paul, one of Sam's favorites. An epiphany, a revelation that smacked him in the face until he was a shivering, bleeding, crumpled-up ball on the floor, and then kicked him a few times for good measure.
That was why he had never loved anyone he had dated. That was why he had never been bothered that he had never had a home, not really. That was why he had never minded raising someone when he, himself, had still been a kid. That was why he would do anything, go into any situation, run into any Hell- metaphorically or literally- for Sam.
Because it was Sam. It was always Sam.
He loved him, and he always, always had.
And really, it was sad that it had taken Dean this long to figure it out.
But to be fair, Dean was... perhaps... maybe... just a little bit thick.
