Of course Dean loved his brother. He loved him with everything he had. But by no means did that mean he could get it up for him, bisexual or not. Sammy was his baby brother. They were blood and blood don't flow south for blood. Not for Dean, at least.
Sam loved Dean in the 'Good God, you're attractive and always protecting me' kind of way. He often had long, intricate daydreams of the day he would finally tell his big brother of his-slightly obsessive- love. Of course Dean would never act first- that would fall to Sam since Dean was so think-headed about his emotions. Anyway, Sam would convince Dean to let him snuggle into his side as they watched tv-it wouldn't be hard, it was a pretty common occurrence, Dean always fell to the puppy eyes- and after a while, Sam would look up at his brother tenderly and place a kiss over the older man's heart. Dean would, of course, be highly confused. But Sam would whisper to him in his sweetest voice
"I love you, Dee, I've loved you for so long, I need you." While Dean sat in shocked silence Sam would press their lips together and they would see fireworks. What followed in the fantasy changed over the years- at first, they would simply smile and Dean would say 'I love you too, Sammy' before going back to cuddling with a kiss to Sam's forehead. Slowly the idea morphed to a second kiss on the lips, to a heavy make-out session, to Sam taking it up the ass from his big brother then and there. Sam jerked off to the idea for years, waiting for just the right time as both he and Dean continued to grow into themselves. Sam assured himself Dean slept around so he could ignore the feeling he held for his baby brother, never considering it might be a one-sided attraction. Despite all the thought he had put into it, his first kiss with Dean didn't go at all as planned.
Dean had saved Sam's life-again- and almost lost his own in the process-again. Once he was healed, Sam showed the anger he had been harboring for the months his brother had been recooperating. There had been a lot of yelling, accusations, and at some point Sam had started to cry.
"Don't you get it, Dean? I need you. If you die I have nothing."
"Stop being such a drama princess, Sam. I didn't die and I'm not going to anytime soon." For a long moment, the brothers simply glared at one another. Then Sam had launched himself across the room, pinning Dean to the wall. Finally, at 17, Sam's fantasy would come true. He pressed his lips to his older brother's and saw fireworks bursting behind his eyelids. Dean just saw red. He desperately wanted-needed- to punch his brother and flee, but he couldn't bring himself to hit the kid. So he settled for a hearty shove. Sam stumbled back a few feet, utterly shocked. "Dammit, Sam! We're brothers! Brothers don't do that!"
"I love you, Dean, I've loved you for years, you're all I've ever wanted, you're all I ever want, please..." As the younger boy spoke, Dean was making a beeline for the door, car keys in hand. "I love you, don't do this to me..." Sam's voice broke and he began to sob, the final nail in Dean's coffin. With a sudden clarity, Dean knew what he had to do, no matter how much it killed him- he could never say no to Sammy. He wrapped his little brother in his arms and quieted his sobbing, rocking gently back and forth. When Sam tried to kiss him again, he didn't fight it. He just opened his mouth and let Sammy take what he wanted.
"We take this slow and you can back out any time you want to," Dean had assured his brother when he finally stopped pillaging his mouth.
"I'll never want that." That was Dean's worst fear, but he just smiled and suggested Sammy take a shower to 'cool off'. As the younger boy bounced off with a grin to do as he was told, Dean's shoulders sank- he could never want his brother like that, but if Sammy needed him he would do his best.
Over the next few weeks Dean quickly established rules for the new aspect of their relationship- nothing below the belt, don't tell anyone. When Sam became sulky because a waitress slipped Dean her number, he promised himself only to Sam, but refused to let his brother do the same. Sam quickly got frustrated and pressed his brother to take things further, so two months into his first relationship, Sam got his first hand-job. He came quickly-which totally worked for Dean- and got angry when he was stopped from returning to favor. Dean placated the young man by allowing him to kiss him-Sam didn't seem to notice or mind that Dean never kissed back- followed by a second hand-job when he was all worked up again. Dean tried to be as passive as possible in their relationship= he didn't kiss back, when he jerked off his brother he really only formed a loose fist and let his brother fuck into it. When that was no longer enough, Dean gave Sam a little more of himself and let him fuck into his mouth. Sam didn't seem to care when Dean choked, or that he never swallowed. Finally the day came when Sam once again needed more. Dean was bordering on clinically depressed, turning more and more to drink for comfort. Sam began to beg his brother to fuck him, and Dean always said no. Eventually Sam got angry and started to yell. Dean took all the abuse silently with hunched shoulders. When his little brother finally wore himself down, Dean gave up the last thing he had been holding onto and stripped while Sam looked on with hungry eyes. Dean crawled naked onto the bed and offered an empty smile to his baby brother, who he still loved so much, despite everything.
"Come fuck me, Sammy." Dean's smile faltered slightly. "Come take me." Sam, for his part, had never considered topping his brother, but found the idea decidedly appealing. He clambered onto the bed and positioned himself between his brother's legs. Dean handed him the lube- generally used during hand-jobs- and allowed Sam to kiss him before flopping, boneless and empty, onto the pillows. Sam worked quickly without thought to any discomfort his brother may have had. Too soon, Sam deemed Dean prepared, and the older man, lost in his own head, didn't object. Dean was forced back to reality as Sam began to work himself into the too thigh space. Sam was gasping at the almost painful grip that just felt so good, and for once Dean was gasping along with him. It went unnoticed by Sam that Dean was fighting tears. Dean fought the pain and let Sammy take what he wanted. It was over quickly.
"So good, Dean. To tight and so pretty and so good for me." Sam had mumbled it into his big brother's chest as he fell asleep. As soon as he was down for the count, Dean made his way gingerly to the shower. He washed a mixture of cum and blood off his aching body, repeating the same thing to himself the entire time- "Anything for Sammy." Time flew by quickly after that- Dean lost himself as little more every day, but he made sure his brother was happy, introducing him to new positions when Sam got bored. When Sam declared his intent to go to Stanford, Dean finally saw a light at the end of a long, very dark tunnel. Animated for the first time in ages, Dean convinced his brother to experience life outside his big brother. Sam left Dean, and Dean fought the consuming guilt he felt when he was glad of it. Six months passed with no contact between the brothers. Dean felt hopeful and fell in love with a beautiful blonde. But one night, Sam called, terribly horny and demanding his brother get to Stanford as soon as possible, so he could 'tap that sweet ass'. Dean was on the road that night, beautiful blonde left behind for good.
"Anything for you, Sammy."