This is my attempt at a one shot (I usually branch off into huge projects but I was determined to keep this below 5 pages). It's Gabriel/Sam with that background Dean/Castiel
I own none of these amazing characters.
Gabriel got away with a lot since making himself at home in Team Free Will. Some of the perks of always getting luxurious motel rooms with separate bedrooms and the good booze usually put Dean at ease, but then again, Gabriel pulled a lot of crap that almost didn't make free Dish Network worth it. That was Dean's opinion anyway.
Sam was between uncomfortable and guiltily turned on half the time because Gabriel was a giant tease. And yes, Sam was sleeping with Gabriel, regularly, but that wasn't the uncomfortable or guilty portion. No. That only happened when Castiel popped in from time to time and Gabriel always greeted his angelic brother with questionable intentions.
First it was touches, and Dean noticed it before Sam did; that when ever Castiel popped in, Gabriel would lean on Castiel's shoulder with his arm while making a long stream of references that Castiel didn't understand, just to watch Castiel's brows lower in confusion; Dean would be stuck explaining what those references were the rest of the day. Then there was the shoves and the pulls, of which Gabriel could do freely because he was in actuality much stronger than Castiel. It all was very brotherly and casual. At first. Of course even then Dean was getting annoyed with how much Gabriel was hanging on Castiel.
Then it escalated and Sam started to notice. Because hugs, hip bumps and smacks on the ass were only so far from the line of 'bromance and no personal boundaries'. They were light and playful, but always something that was hard to miss. It always earned Gabriel an agitated grunt or glare from Dean which Sam could see was only feeding Gabriel's instigation meter. Castiel took it surprisingly well; slightly confused though. Of course Gabriel was always presenting Castiel with a verbal distraction to hide out of the blue contact.
Then there was a very large step over the line of 'incestuous misconduct'; it happened several minutes after a tiff between Dean and Gabriel about music and that Gabriel would NOT snap on any music he felt like when he was hitching a ride in the Impala. It happened when Castiel was sitting in the back seat with Gabriel and Gabriel leaned over and kissed Castiel on the neck. And it wasn't just a peck, it was one that Gabriel pulled Castiel over for and tasted skin for a good 5 seconds. Dean's eyes bugged out because he saw it in the rear view mirror, Castiel's face turned an hint of pink, and Sam turned around just in time to see what Dean was bugging out about. Dean pulled the Impala over so fast he nearly careened into a tree and very animatedly demanded that Sam and Gabriel switch places because Sam and Gabriel were not allowed to be in the back together (No making out in the backseat rule), and now neither were Gabriel and Castiel. Gabriel was rather smug in the front seat because Dean's face was a furious red and his knuckles were a ghostly pale on the steering wheel. Sam and Castiel were the quiet ones in the back.
Sam was conflicted because well... it was a little hot to see two angels touching inappropriately in the back of the Impala. And yes, it would have been appropriate to be angry at Gabriel for kissing another man's neck especially when Gabriel and Sam were dating, lovers, ect. but he found himself more flustered than angry because he knew Gabriel was not serious. It was all to get back at Dean, because Gabriel and Dean were childish like that.
And Gabriel did not stop once he got the hook in Dean. He had found Dean's disdain and prodded it like an open wound. Because Dean and Castiel were always dancing around each other like some sort of awkward waltz and no fair amount of talking or reasoning would get either Castiel or Dean to face each other about it. Gabriel and Sam knew this because they had tried until they just gave up.
But it seemed Gabriel had found a new tactic; jealousy and possessiveness. So, kisses and nips on the neck made Castiel flush. A smooch on the cheek, pats on the rear, hands lingering far too long on Castiel in any way. Dean acted when he saw this, always pulling Castiel away.
"God, Cas, you can tell him to STOP."
"I don't mind, Dean, really."
This always put Dean in a worse mood, but still corralling Castiel away from Gabriel, who didn't linger after that; he always returned to Sam to enjoy the show. Sam wasn't sure exactly why Castiel didn't mind his angelic brother touching him, but it sort of made it worse for Sam because Sam liked the idea of Gabriel and Castiel making out. Which he knew was an awful, terrible, horrible thing to even think so he never mentioned it but he always watched.
"Enjoying the show, Sam?" Gabriel waggled his eyebrows at Sam who nearly choked on his beer, thinking Gabriel knew he liked it. Sam had made no mention of this to his lover.
"Oh, um... they're talking at least." Sam muttered, holding his hand over his nose, where beer had almost escaped. Gabriel smiled and hopped up on the table that was next to the chair Sam was sitting in. Sam fiddled with the bottle as Gabriel leaned his chin on Sam's head and draped an arm around Sam's shoulders, "Um... don't you find this... weird?"
"What weird?" Gabriel tilted his cheek on Sam's soft hair.
"That... you're essentially molesting Cas?" Sam watched Dean and Castiel watching TV on the flat screen on the wall. Both were on the couch, and Castiel was practically being squished into the arm of it by Dean. But Castiel, again, didn't seem to mind. Gabriel chuckled.
"Are you kidding? It was Cassie's idea to continue doing it." Gabriel patted Sam's chest and Sam turned to look up at Gabriel, confused.
"What?" Sam said and Gabriel pointed to the two on the couch, where Dean's arm was roped tight around Castiel's shoulders, pulling him to his side.
"Don't you see how much attention he gets from Dean after Dean get's ticked off?" Gabriel pointed out, leaning his forearms on Sam's shoulders and one hand slipped under Sam's t-shirt, playing along the hunter's collarbone. Sam rested against Gabriel's chest, "And plus watching that color on your brother's face amuses me too much." Sam smiled a little, that part was pretty funny, "And Castiel's still getting used to the whole enjoying touch part. I don't think he particularly minds where it comes from, but he'd like it to be more from Dean." Sam drummed his fingers on the glass of his beer, which was empty now.
"So, he doesn't mind his big brother is well..." Sam felt Gabriel shrug against his back and head.
"Well, frankly, his vessel is nothing related to my vessel, so can you really call it incest?" Gabriel theorized and Sam shrugged awkwardly.
"Well... still, angel brothers."
"Ah, well." Gabriel grinned, Sam could hear it, "I also enjoy teasing Cassie because it turns you on." Sam's face felt hot suddenly and the glass bottle hit the carpeted floor with a few thunks. Dean and Castiel didn't even glance up from their TV program.
"I uh... I don't, I'm not..." Sam swallowed and Gabriel chuckled, his hand going further down Sam's shirt.
"Oh shush, you find it hot and you know it. I mean, your face after I kissed Castiel in the car was priceless. Not to mention you never get mad at me." Sam threw Gabriel a scrunched up face, but he knew it was far too late to start acting now, "You have to admit, you're just a little bit of a perv."
"I'm not." Sam denied. Because Dean was the one always watching porn and confusing it with the real world. He was just... simply ignoring the fact that two angels mocking incestuous misconduct was a little bit hot to him. It didn't make him a pervert.
"Just a little bit." Gabriel persisted and his fingers toyed with one of Sam's nipples, which Sam tried to ignore, "I mean, nothing like me, but you can't say you're Saint Samuel." Gabriel's tongue touched Sam's ear and Sam shuttered, "I know you're a wild cat in bed..."
They were distracted by a soft cover book hitting the table Gabriel was sitting on and Dean scoffing, "Get a fucking room you two."
Gabriel picked up the book, shaking it at Dean, "You watch what you throw of mine, or I'll throw something of yours." He warned and drew his hand out of Sam's shirt to snap his fingers, popping both Sam and Gabriel into Gabriel's personal suit in the inter-dimensional house he basically had made as Team Free Will HQ, "Now," Gabriel's hand returned to the nipple under Sam's shirt, now kneeling behind Sam on the large queen size bed (which could be a king size, but he just found the queen joke amusing), "what is it about your little angel fetish?" Sam flushed and smacked Gabriel's hand to get him to stop because it was distracting.
"It's not a fetish." Sam defended and frowned as Gabriel was relentless, switching hands in his shirt to get the other nub, "It's just... I don't know, kind of... stop that." Gabriel did not 'stop that'.
"It's hot?" Gabriel grinned, "Me hitting on Cas? Thinking about me making out with him?" Sam didn't answer because he could not properly deny that when Gabriel was pressed up against his back and really close to his ear, "Getting all handsy with him? Kind of like this?" Gabriel's free hand slid down Sam's back, over Sam's abs and belly and his mouth kissed his nape. Sam bit his bottom lip.
"Okay, okay, yes. It's just... you wouldn't actually do it, would you?" Sam ventured awkwardly.
Gabriel scoffed into his neck, "Pfff, Hell no, he's my brother." Gabriel rested his chin on Sam's shoulder, "Just like I wouldn't mind if you and Dean made out either." Sam felt like he had a bucket of cold water dumped into his lap and he spun half around on the bed to look at Gabriel
"You're not serious."
"Oh hush, Sam, you have fan girls who've posted it all over the web." Gabriel waved it off, "And pictures too."
"Don't remind me." Sam's head fell into his hand. He was slightly scarred from that experience.
"I'm just saying." Gabriel slithered down Sam's body, sliding his back into Sam's lap and his hand slid down Sam's jaw, "Nothing to be embarrassed about. human sexuality is a fickle thing." Sam looked down at the archangel, running his hand idly over Gabriel's chest.
"What about angel sexuality?" Sam asked curiously.
"Pretty non-existent," Gabriel shrugged, "s'all 'soldier on, soldier on, ignore that feeling, and that one'. Not fun until we get a vessel and a bit of freedom. You get the picture. I think I can fill books upon books about that subject." Sam then glanced at the book that Dean had thrown at Gabriel and blinked, picking it up. It was a Supernatural book, titled, 'Tall Tales.'
"Oh God, you're not a fan too, are you?" Sam asked and Gabriel smirked.
"Got every single one." Gabriel bragged, "Especially all the ones with me in them."
"Psh, of course." Sam flipped through it, finding some of the pages hi-lighted, "What the... 'Sam gave the janitor a rare and genuine smile for all the witty jokes he said as he showed Sam and Dean the office of the dead teacher. He found the man charming and easy to be around'. What is this?"
"I just like to point out when you started flirting with me." Gabriel poked the spine of the book, "Chuckles cut out all of the bits where we had sex, unsurprisingly." Sam flushed, "He's going to regret that when ever he adds more. Did you know that we have a small but loyal following as well? Pictures and everything." Sam blinked.
"What?" Sam dropped the book to look at Gabriel, "Since when."
"Ah, 'Mystery Spot', actually." Gabriel took the book and closed it, "You know, the whole trying to prevent you from making the biggest mistake of the Apocalypse." Sam fidgeted with his fingers in Gabriel's shirt.
"No one is going to let me live that down."
"You dun fucked it up." Gabriel shrugged, "Over it." He dragged Sam down by his shirt, kissing him, "In the process of fixing it." Sam smiled slightly.
"So... Do you think Dean'll ever get the hint?" Sam asked casually enough and Gabriel shrugged.
"Dean's kinda dense." Gabriel smiled wryly, "Just gives me more time to give you a show." Sam flushed a nice red, his eyes darting back and forth and Gabriel patted his cheek, "Easy, Cas and I have agreed to not have mouth to mouth contact." Sam tried not to feel a slight loss in that fact.
"Right, got it." Sam said but he got his own lip contact with Gabriel so it was okay.
It didn't last much longer, it seemed the last touch to trigger that final decision out of Dean was the simplest hand on Castiel's shoulder; when Gabriel wasn't even trying to be flirty. Dean may as well have huddled Castiel away and screamed "MINE!" at the top of his lungs for the way he took Castiel's arm and kissed him hard on the mouth whilst at the end of a hunt when the two humans were all tired. Dean didn't say a word though, and Sam ended up timing the lip lock after a few moments, because Dean wasn't letting go; and Cas was holding on tight. A minute and a half was a lot for a first kiss and Sam did not feel uncomfortably turned on by this, which was a relief.
"I think you're just turned on by me." Gabriel concluded while laying on the hood of the Impala as they watched Dean and Castiel work it out with that look they always gave each other.
"Maybe." Sam smiled, pretty okay with having Gabriel to himself again; and he got a kick out of asking Dean if he and Cas wanted to ride in the back seat. And Sam called Dean a hypocrite when Dean said yes.