Ok, there are plotty reasons why this is all ok, but to reveal them now would ruin the point – so you'll just have to trust me. I had this idea after reading another fic and was left with the idea that Castiel makes a much better brother than Sam. So yes, whilst this is technically an incest fic, it does have a point and I'll try not to let it be weird.

Dean's parents died when he was six. His brother, Castiel was only four. Within a year he'd forgotten that John and Mary Winchester were his parents. From then on he knew only that he lived with his brother, Dean in the Weston Children's Home, and had done for all his living memory.

It wasn't the worst childhood. Dean and Castiel shared a room, sleeping in the same sagging double bed every night. During the day they were inseparable, Castiel followed Dean wherever he went and Dean always made some time just sit in their room so that Castiel could read without worrying where he'd gone.

A few of the kids found them weird. Dean was a product of his father's influence. Named for James Dean, raised for his six years to believe in hard work and family. Castiel was the youngest, babied by their mother, named for the angel of his day of birth, he was introverted and devoted to his older brother.

It didn't bother either of them that they had no friends outside each other. Castiel didn't notice and Dean didn't care.

Dean is 12 - Castiel is 10

A bed opens up when one of the kids get's adopted. Castiel moves down the hall, his books disappear from their shared shelves, his clothes vanish from the closet. Dean sleeps the way he always has, on his back, on the right side of the bed. Except now Castiel isn't there, curled on his side facing the wall.

He worries about him.

It turns out that Castiel can't sleep without Dean. In fact he can't remember a time when he and Dan haven't shared a room, or a bed. For three nights he doesn't sleep, just lies in his new bed and wonders what Dean's doing, if he's awake and somewhere else.

After the fifth night Dean starts to notice.

"Cas! Hey, Cas?"

His brother's eyes which have glazed over in front of the TV, snap back to attention. He's pale, almost grey and the dark circles under his eyes are deep grooves of shadow.

"What?"

"You ok? You look like a zombie, man."

They're sitting with their backs to the couch, Castiel leaning slightly against Dean's side and picking at a hole in his T-shirt.

"Jus' tired." He lets his eyes close and sags further against his brother, falling asleep for the first time in days. Dean rubs his hand against Cas's spine and goes back to watching Batman taking out the Riddler.

That night Castiel finds his room emptied of his things. He cracks open the door to Dean's room and see's all his books and possessions back exactly where they used to be. He crawls into bed beside his brother.

Castiel sleeps properly and dreamlessly. Dean realises how tense he's been, the second he feels Castiel weighing down the mattress he relaxes. His family is beside him again.

Neither of them mentions moving out again.

Dean is 14 – Castiel is 12

The first time it happens, Dean wakes up at four in the morning with loose limbs and a heated spreading dampness on his thighs. The details of the dream have already faded, something about a redhead with pale skin, but its effects are obvious. Feeling sated and more than slightly ashamed he shrugs off the sheets and gets up, heading for the washroom.

Castiel stirs.

Dean waits, not daring to move, he can't stand the idea of his brother waking up and seeing this. He's never been shy about his body before, not with them sharing a room, but now he is. He's acutely aware of his coarsening body, the first signs of hair and muscle that separate him from Castiel, because he's still a child and Dean isn't. Tonight is the last straw, the dream that left him arching into the damp spread of come on the sheets. He's changing and he hates it, because Castiel won't understand.

He doesn't wake up.

Dean gets to the washroom, cleans up and creeps back to the bed. With a handful of crisp paper towels he scrubs at the dampness on the bed, hoping it hasn't seeped into the box spring. Castiel moves, opening his eyes to the slant of light from the bathroom door and the sight of his brother.

"Dean?"

It's quiet but he still jumps guiltily and snatches the soiled paper behind his back. Castiel frowns sleepily at him.

"What's..." He casts a bleary gaze over the bed, catching on the small but obvious dark place on the sheet, taking in Dean's boxers, clean ones that he wasn't wearing when they got into bed. Dean's face burns with shame and disgust. Castiel shouldn't see things like this. Shouldn't even be in the bed with him now that this is happening.

His brother's face doesn't crumple with disgust though, or even with curiosity. He just takes in the little details of the scene in front of him.

"Oh" he huffs in understanding, and just like that he settles back into the bed, not turning back onto his other side, but watching Dean. His eyes making clear the message – Hurry up and get back here so I can go back to sleep.

Dean unfreezes himself, tosses the paper towels into the trash and gets back into bed, avoiding the damp patch. It puts him slightly closer to Castiel than usual, and for a second he's worried, it might happen again during the night and he doesn't want it to be near or on Castiel. His brother makes the decision for him, moving closer until his head is resting against Dean's shoulder.

"Night" he mutters sleepily.

It happens again a few nights later, more often after that as the advent of puberty progresses. Dean grows taller, broader and his voice begins to break, much to the amusement of everyone at the home. The light dustings of hair on his body grow thicker and darker until eventually he forgets what it was like to be smooth and fragile.

Every time he wakes up, sweating and half moaning into the mattress with release, it wakes Castiel too. After a while it stops being awkward, he forgets that there was a time it didn't happen. Castiel accepts it for what it is, like he accepts everything else about their life. Because it's Dean, and nothing of Dean could be strange to him.

Next to Cas, Dean finds he looks a lot older, more than ever he tries to look after his little brother. Now that he's growing up, growing stronger, all that strength is going into being Castiel's guardian. He knows he can't replace his father, a man he can barely remember, but he tries anyway.

Dean is 16 – Castiel is 14

Dean's first girlfriend it a cute redhead called Anna. She's in his fourth period biology class and she's the only thing that keeps him from skipping it.

They've been dating for three months before she points out that she's never seen his house. She knows he lives at the home, but she still wants to meet his 'family'.

Bobby and Ellen are nice enough people, Dean has no misgivings about introducing her to them. Its Cas he worries about, that and their living situation. He's now very aware that there's no reason for them to share a bed, that it's plainly weird. He doesn't want Anna meeting Cas and freaking out.

He already got a weird visit from his social worker who pointed out in no uncertain terms that Castiel should have his own room. There's no way Dean can explain that it's normal, that it's nothing weird. Cas just likes having him around and Dean likes keeping an eye on him. Even the other kids, the ones who've been there for years, accept it as perfectly fine. Though the new arrivals avoid the Winchester kids and give them weird looks when they fall asleep together on the couch or on the rare occasions they hug. Because despite the way they sleep it's unusual for them to touch.

He takes Anna to the home anyway, introduces her to Ellen and Bobby and the kids (Ash, Jo, Ruby, Meg and Madison.) Castiel is in their room reading so Anna meets him last. He shakes her hand nervously, but with genuine warmth.

"Hello"

"Hi, Cas right?" inwardly Dean flinches, the only fight Castiel has ever been in was over the use of his nickname. Though personally he thinks Michael was a douche for using it, and a douche pretty much all round. Castiel makes no comment, it doesn't seem to bother him.

"So...this is your room?" There's more than one question there.

"Actually" Castiel cuts over Dean "Dean's room is down the hall." As he ushers Anna from the room Dean shoots a questioning look at his brother. Castiel just shrugs and smiles, a little sadly.

The room down the hall, the room that was Cas's for a week years ago, is now filled with Dean's stuff. Castiel must have done it earlier that day, but it looks lived in, there's even laundry on the floor.

Even when Anna pulls him into a reasonably engrossing make out session, Dean can't stop thinking about what Castiel's done for him. He not only gets that most people are squicked out by the idea of them sharing a bed, but he cares enough to make a room up for him so that he doesn't have to explain it to Anna.

He doesn't have to ask why – Anna makes Dean happy, so Castiel would do whatever he could to keep her around. He'd done the same with Michael, who had been Dean's friend for a while when he first arrived. Because of that Cas had kept the bruises covered up, hadn't told him all the ugly things Michael said to him until Dean caught them fighting. The one and only time Cas had hit back.

"You should have told me" He'd raged afterwards, dabbing at the cut over Cas's eye.

"You liked him." The way Cas says it shows he thinks it a good enough reason to take a few beatings in silence. Just to keep Michael around for Dean's benefit.

"I like you more." He'd said, quietly, still focused on cleaning his brother up.

And the weird thing is that he likes Castiel more than Anna as well.

He likes Anna, he really does, because she's nice and smart and has a fucking awesome sense of humour. But then he gets all that from Cas, the only thing he needs from Anna, the only thing he gets from her that he can't get from Cas, is sex. It makes him feel guilty, incredibly guilty, because if it weren't for his libido he probably wouldn't be with Anna. It's hardwired into him that he only needs Cas, and so what he can't get from, and doesn't want from Castiel, he has to find elsewhere.

He breaks up with Anna a month after the visit, not telling her that he does it because she deserves better. Because she's an awesome girl, and better than being just a lay.

He keeps his things in his new room, using it for the other girls he brings home after Anna. Girls who are alright, pretty hot actually, but not girls he likes, or has fun with. He's learnt his lesson there. So he gropes them on the single bed, gets pretty far with some of them, and eventually loses his virginity there too.

But he still sleeps down the hall in the shared bed, and Cas never questions it.

Dean is 18 – Castiel is 16

Castiel groans in his sleep and wakes Dean up, leaving him blearily conscious but still half in his own dreams, wrapped in almost suffocatingly hot sheets. He's almost convinced he heard nothing, and is allowing his heavy lids to close, when the sound comes again. Castiel's groan, broken with need and roughened by the fact that his voice has changed.

Dean recognises the sound and inwardly kicks himself. He should have expected this. Cas might be going through puberty late but he has been going through it. Dean's noticed the height he's gained, gangly as ever, and the prickling hairs along his legs that catch at Dean's occasionally beneath the bed sheets.

Beside him Cas's breath comes, shallow and rasping into a frustrated whine. It's either his first wet dream or the first really vivid one, because Dean hasn't noticed anything before. He doesn't know what to do, but feels weirdly protective of Castiel and oddly affectionate at the same time. From the sounds of things this is going to be so good for him, and that almost pleases him, until he realises how strange that is.

Cas gasps and arches with a strangled groan, flopping onto his back and opening his eyes. His hips move languidly beneath the sheets, sweat sheens his shaking body. Dean waits for the shocks to subside, until Castiel comes back to his senses. He looks shaken, confused and not a little freaked.

Dean edges gently closer and lays his head on Cas's pillow, nudging his mouth against Castiel's ear.

"You ok?" It comes out gruff, his voice rasping into the quiet. Castiel nods shakily, looking anything but. Dean isn't surprised, it's not like his brother has shown any interest in sex, any indication what so ever that he does anything in the shower besides shower, or that he likes anyone or anything in that way at all.

He huffs a breath against Cas's shoulder, feeling his brother bury his face in his sleep tangled hair, still coming down from his orgasm. Which was probably his first. Dean lets him lie for a few more minutes, then shifts him gently.

"Go get cleaned up." He whispers, watching as Castiel slides out of bed and through the dark towards the washroom. When he gets back, Dean stays close to Cas's side of the bed, lying close but not touching.

Cas's dreams are not as frequent as Dean's used to be, but they are more intense. He almost always wakes Dean up by moaning or mewling in his sleep, and his release leaves him shaken and needy. Every time it happens Dean slips over to his side of the bed and lies close to him, 'warming him up' he thinks, irrationally because if anything Cas needs cooling down. In reality he just needs to be there for his brother when he's vulnerable, or in need of comfort. And it's in the time after his intense orgasms that Cas is the most vulnerable Dean has ever seen him. All wide eyes and messy, sweat soaked hair. It stirs a painful surge of something in his chest.

It's around this time that Dean turns 18 and leaves the home. He's old enough to be Castiel's official guardian, old enough to get a job and move them into their own apartment. Initially they get a one bedroom place because it's cheap, and they don't really need a second room, not now Dean isn't bringing girls home from school. If it comes to that he figures Cas can just sleep on the couch.

Their social worker visits a week after they move in. When he sees the solitary bed he does a double take. Inwardly Dean curses, knowing that he should have thought this through. As brothers he and Castiel could almost get away with sharing a bed. Now he was Castiel's guardian and allegations could and would probably be made if it looked like he was taking advantage.

He saw the social worker, Zachariah Phelps, take in Dean's tall, broad frame and then Castiel's much thinner body. Sure there was only a two year age difference, but Dean looked like he had at least five years on his brother.

Zachariah tightly informed him that it might be wise to get Castiel his own room. There followed a brief interval while Dean waited for the social worker to talk to Cas, probably giving him the 'show us where he touched you' speech. His stomach dips suddenly when he realises how their post-...well post wet dream petting is probably not something that would go down well. Especially not with Zachariah who looked like he'd been disowned at birth.

Castiel doesn't give anything away, not that there is anything to give away. But somehow Dean is less sure of that than he used to be, he knows what they're doing isn't wrong. But it is moving further away from what's normal in everyone else's eyes.

It's not like he can love Cas less.

When Zachariah finally leaves, Castiel edges into the living room and sits next to where Dean is sprawled on the couch. His dark hair is spiked up in all directions where he's run his hand through it in thought.

"So I guess we're moving." Dean sets the remainder of his beer aside and rubs a hand across his face. He really doesn't need this shit right now, not with his pay check stretched as it is. He's only a bartender, how the hell is he supposed to afford a bigger apartment and keep them both fed and the heating on? For the first time he wonders if Castiel might be better off back at the home.

"Can we afford it?" The little mindreading bastard.

"No, but I'll work something out." He says, with more confidence than he feels. Castiel says nothing, just goes to make them both dinner. He's good at that, better than Dean anyway. Since he turned sixteen it's been less 'Dean taking care of Cas' and more 'Cas and Dean getting things done between them' less punchy but it's a nice change.

Which is why it shouldn't surprise him when, next evening, Castiel comes homes with news.

"You did what?"

"I took at job at the diner near the police station." He breezes around the kitchenette, setting up plates for spaghetti.

"Cas..." he struggles for a second "you...you didn't have to do that. I can take care of you, ok?"

"And this makes it easier." He shrugs, stirring one of the pans vigorously and pointedly ignoring Dean.

And ok, it's a good idea, and definitely a weight off his mind, but he can't shake the feeling that he's failed somehow. Castiel is his to look after, has always been his responsibility and he likes doing it. Dean likes feeling needed. But then he has to admit that maybe Cas feels like it's a bit one sided. Which is crap because he's giving Dean a lot just by being there. It's all too hard to explain so he settles for changing the course of the conversation.

"Bitch"

Castiel half turns with one of his rare, full on grins. For a second he looks so grown up that Dean's stomach twists in surprise.

"Assbutt."

Dean is 19 – Castiel is 17

"How was work?" Dean yells from the couch. He has to yell now, the apartment is just slightly bigger than the last one. Castiel toes off his shoes and collapses on the seat beside him. His T-shirt is sticky with sweat and there's a mark on his jeans. He looks completely exhausted.

"Alright." He murmurs noncommittally. Dean just passes him a beer from the side table. Castiel unscrews the top and they both return their attention to the action movie playing out on their portable TV. After a while Castiel yawns.

"Tired?" Dean asks, pointlessly.

"Just a little." He blinks to clear his eyes. "I think I'll go to bed."

Dean can't help feel guilty. After the visit from Zachariah he and Castiel had managed to land a new apartment, one with two bedrooms. They'd been living there for a few months now and Dean was getting the distinct impression that Castiel hadn't had a good night's sleep for almost as long. Between that and the double shifts he was working just so they could afford the place he was beat most of the time.

He was also never going to say anything. Castiel was stupidly heroic about his own suffering and would probably keep quiet about a broken limb if it meant saving Dean the grief. Add to that how paranoid Cas was that Zachariah would split them up and his brother was probably never going to sleep again.

Dean cleared his throat and briefly wondered why this felt like asking someone to spend the night with him.

Possibly because kinda was.

"You want me to..." Cas looks at him, grateful and hesitant all at the same time.

"Yes" he manages, drily.

"Ok...I'll be there in a minute."

He turns off the TV, sets his dishes in the sink and goes down the hall to Cas's room. He opens the door just in time to catch him stripping off his soiled T-shirt. Already down to his boxers. It's a combination of the sight of the muscles moving in Cas's back, and the light evidence of stubble that shadows his face and neck that starts the thought going. It's not until they're lying in the dark that Dean realises why it seems weird.

He can't pinpoint the moment Castiel stopped being a kid, but he has. The man lying next to him is just that, a man.