Chapter Text
James Potter would never, not in a hundred years, do anything to hurt his best friend Sirius Black.
Sirius was his brother, his platonic soulmate - the one person who would never leave him.
Because of that, he would never do anything that would hurt Sirius – really hurt him. James had no problem grinding down the last croissant at breakfast, even though he knew Sirius wanted to eat it (sometimes he even ate the croissant even though he was full, because he found it funny when Sirius yelled in his drama of betrayal and the end of a friendship).
And so far there hadn't been anything in the world that had shaken James in his resolve – at least not until after graduation he'd moved in with Peter, Remus and Sirius and a flat in London that now served as the first port of call for their friends . Their friends and Regulus Black, who had also finally broken away from his family after his nineteenth birthday four weeks ago, who now lived in a small basement apartment nearby and dropped by the apartment from time to time.
Regulus and Sirius didn't have an easy relationship, even for brothers. Most of the time their conversations ended in shouting and Regulus stormed out of the apartment while Sirius complained about having an ungrateful asshole for a brother.
Still, they loved each other, somehow. Sirius would never admit it, but he would give anything for Regulus and destroy anyone who dared harm his brother.
And James admired this messy family love and Sirius' willingness to stop at nothing when it came to his brother. He really did.
There was only one problem:
Regulus Black - the little arrogant prick - was hot as hell.
In the two years that James hadn't seen him, Regulus had gone from a typical annoying Slytherin with a cocky grin and God complex to an attractive, seductive young Londoner with a cocky grin and God complex, and James was just a weak, poor man.
And Regulus knew that.
He knew he was hot.
He knew James had a hard time resisting him.
He knew Sirius would kill James if he even laid a finger on Regulus.
Despite this, or perhaps because of it, he flirted with James every free minute.
Whenever they stood alone in the kitchen cooking, Regulus would lean over James' shoulder and whisper something about admiring his filigree handwork, then innocently point to the chopped vegetables James was working on.
Or, after James's shower, he'd slip past him into the bathroom and mutter something about water-saving suggestions.
Or, and this was the worst torture of all, he would wedge himself on the couch between James and Peter, spread his long legs across James' lap, and let his pointed fingers scrape James' skin whenever nobody was paying attention to them.
Maybe that was one thing dysfunctional brothers did - flirt with your brother's best friend because you think he likes him more than you.
Or maybe Regulus was just enjoying the fact that James squirmed under his gaze, unable to stop it or take it to the next level.
Whatever it was, it drove James crazy.
Because he didn't want to hurt Sirius, which he would if he succumbed to Regulus.
Regulus was still Sirius' little brother, after all. Little Reggie, whom he loved so much but also hated so much, and who looked just like his mother, but was also so different from Walburga.
But for James, Regulus Black was both the forbidden apple and the serpent on the tree of Eden, and James was weak. Weak in the face of Regulus Black's beauty.
James was lying on his bed, eyes closed and his hands loosely clasped in front of his stomach, when someone walked into his room.
"Hey, pretty boy," Regulus purred – James knew it was him without looking because only Regulus called him that. "What would you think if I lay down with you?"
James swallowed hard before sitting up and grabbing his pillow to hold it against his chest like a shield. "I don't think Sirius would like that."
He looked at the door, where Regulus was leaning and chuckling – Not a good idea.
Regulus was wearing a dark shirt, sleeves rolled up, and slim pants that fitted perfectly at the hips and made his butt look extra good.
James wanted to die. He wanted to smother himself with his pillow and die because all he could think of was ripping the shirt in two and spreading bite marks across Regulus' chest.
"But you'd like it?" Regulus asked, chuckling, pushing himself away from the wall and slowly walking towards James, who gripped the pillow a little tighter. "Sirius isn't here, you know. Actually, no one is here except you and me."
"Where are the others?" James couldn't help but sound scared. He had never been alone with Regulus before. He was ashamed of it, but the first thing that came to mind was that Sirius didn't need to find out.
"I don't know where Peter is. Work, maybe.” Regulus stalked on, like a jaguar stalking its prey. "Sirius and Remus are on one of their awful dates that Sirius always plans weeks in advance."
This meant that they would come back late because they would be busy all day and they usually went out to a restaurant in the evenings. And Peter worked until five o'clock and then visited his mother for half an hour.
That meant James had to endure at least another three hours alone with Regulus - Regulus, who sat down next to him on the edge of the bed and buried his fingertips in James' hair.
"You have to go," James demanded, not sounding very polite.
"I just got here." Regulus grinned wickedly and edged a little closer to James, who was clutching the pillow shakily. "Wouldn't you like to offer me some tea?"
James closed his eyes and remembered Sirius, who was his best friend and whom he would not hurt. "No, you have to go. Sirius isn’t here.”
"You know, Jamie, one might think you don't like me very much." Regulus mock-pouted and rested his head on James' shoulder. "Shouldn't you like your best friend's brother?"
"Regulus-" James ground out, unable to push him away.
It was unfair that the hottest guy in England who was interested had to be his best friend's little brother. Why couldn't it be a stranger? Or even Snape? Sirius would be less angry if James slept with Snape because Snape wasn't his damn brother.
"Be a good host and entertain me until my brother gets back, will you?" Regulus purred - surely enjoying how distraught James was.
"Reggie-" James' voice was shaking and he had to refrain from tossing the pillow across the room and finally pressing his lips against Regulus's. "Please-"
Regulus laughed, low and mean, and James trembled because even Regulus' meanness was seductive. "Mh, I think I like it when you beg," he whispered in James' ear, running his fingertips down James' thigh until he reached the pillow that James was holding against his private parts. "But I also think I know a much better job for your mouth."
That was the end.
James was only a man too. He'd endured almost four weeks of flirting and attempts at seduction, and that should be worth something.
He just couldn't be asked to hold back any longer while Regulus pushed him to the edge over and over again.
Sirius who? There was no one left in his head to tell him that this was all a shitty idea. Not a best friend he betrayed. No morals. Nothing.
There was only Regulus taking the pillow from his fingers and pushing him back onto the bed.
Regulus, who straddled him and leaned forward until James could feel his hot breath on his neck.
Regulus, who grinned wickedly, and finally covered the last few inches and pressed his lips to James's.
The serpent had won - James plucked the forbidden fruit from the tree and it was delicious.
Regulus' lips tasted of coffee and scotch - Sirius had once said that Orion always drank scotch and James wondered if Regulus had learned it from his father at some point or if drinking scotch was just a Black-thing to do.
James had to stifle a startled gasp as Regulus snapped his teeth at James' lips. He could feel Regulus' wicked grin on his lips as he licked the bruised area with the tip of his tongue and all he could think about was more.
He let his hands, which were clenching the mattress, carefully run down Regulus' thighs, down his waist to his buttocks, which he gripped tightly. Regulus moaned - which was a new sound and went straight to James' hard cock.
"Take it off," Regulus demanded, sitting up again, arms crossed over his chest. He looked like an icy prince seated from his throne, only the crown was missing. "Your shirt, take it off."
James could only nod and tried to pull the shirt over his head as fast as he could. It was quite a struggle as James was still lying flat on the mattress but Regulus just watched him and didn't even try to help him. When he finally got rid of his shirt, Regulus stroked his bare chest gently and carefully, exploring every bump and mole with his fingertips, and finally leaning in again to plant hot kisses down James' jaw.
"Your shirt," James croaked, utterly breathless and hoarse. "May I take it off you?"
"I'll do that," Regulus explained. His voice was still clear as if he didn't mind the making out and James' hard cock up his butt. "You may open my pants."
James just nodded and jerked at the button of his pants with trembling fingers as he watched Regulus undo each button of his shirt one at a time, exposing more and more skin. His mouth went dry as the shirt finally slid off Regulus' shoulders while he still hadn't managed to unzip the pants.
It was embarrassing, but the sight of the half-naked Regulus Black on his lap made James feel like a fifteen-year-old virgin all over again, about to cum in his own pants.
"You're not going to fuck me today, Jamie," Regulus breathed while kissing James' chest. He kept biting the sensitive skin, licking it with the tip of his tongue and laying his lips on the spot - James was secretly hoping the treatment would leave marks he could later examine in the bathroom mirror. "But you can eat me up."
James groaned - apparently he liked being pushed around by Regulus (which was something new he was learning about himself) - and nodded. "Yeah. That sounds good."
"Is does?" Regulus chuckled and kissed him on the mouth again. "Come on then, pretty boy."
That's all James needed to roll over the mattress with Regulus to lie on top and he immediately started kissing Regulus' jaw and digging his fingers into the black curls.
Regulus still hadn't lost his smug grin – Like a prince who's been taught to keep his composure, he lay beneath James, his hair spread out on the mattress. James wondered if he could make Regulus lose his composure.
"Don't get distracted, Jamie," Regulus demanded, grabbing James' hair to push his head further down. "You already have a clear goal."
"I’m not getting distracted," James mumbled against Regulus' belly button and (finally) pulled his pants off his hips. "I'm on an adventure."
Regulus laughed again, but this time it sounded a lot more honest than the mean giggle he usually let out. James booked that as a win.
With trembling fingers he pulled down Regulus' boxer shorts and let them fall next to the bed along with the pants. His breath was ragged as he pushed Regulus's legs apart and sank down between them. He could feel Regulus keeping a close eye on him and that made him so much more nervous because he wanted to do well.
James had been with others - men, women, non-binary people. With some he had only spent one night, with others he had gone on dates and had relationships, albeit mostly short ones.
But none of them had driven him as crazy as Regulus did. None of them had ever unsettled James so much.
Regulus' thighs were light and warm and James couldn't resist sucking and biting at the thin skin while Regulus sighed contentedly above him and buried his hands tightly in James' hair. He clawed his own fingers into Regulus's waist, hard enough to bruise him but he wouldn't know what else to do with his hands.
"Merlin, you're beautiful, Reggie," James whispered, unable to think of anything else. "And so hot. Shit, you're damn hot."
"Don't stray, Jamie," Regulus reminded him, guiding James' head back to its place between his legs, although his cheeks were slightly flushed and his voice even shook a bit. (Another win)
James kissed Regulus's bite-covered thighs one last time, then (finally) turned to his cock.
He licked the tip as a test before enclosing it completely in his mouth. He suckled, nibbled, licked while Regulus moaned loudly, though not indignantly.
When he finally let go of the cock and instead sank the tip of his tongue into Regulus's hole, followed by first one and then a second finger, Regulus gasped in surprise.
His grip on James' hair tightened and he wrapped his legs around James' neck to hold him in place.
Regulus' thighs were now pressing hard against his ears and all James could breathe was Regulus.
James stayed between Regulus' legs, alternating between his swollen cock, which he licked, sucked and bit, and his hole, which he worked with his fingers and tongue until Regulus moaned to orgasm.
He licked Regulus' oversensitive cock one last time, carefully disentangled himself from the leg grip and climbed back up to plant a kiss on the crook of his neck, vaguely hoping for a word of praise from Regulus (which was also new to James, until now he never wanted to be praised)
"Mm, yeah." Regulus purred and pulled James' chin in to kiss him. Surely he could taste himself on James' lips, but he didn't even flinch. “You are a good host, Jamie. So caring.”
"You're so pretty, Reggie," James replied. He didn't even try to respond to Regulus's flirting, especially now that he was gasping for breath because he had almost choked on Regulus' cock. "You make me weak."
"Yeah, I had a very easy time with you," Regulus admitted, grinning wickedly, rubbing James' lower lip with his thumb. "First time we're alone and I already have you in bed. I really thought this would take longer.”
James groaned and pressed his face into the pillows. "Do not remind me of that. Merlin and Morgana, I wanted to hold back."
"Well, you didn't." Regulus nudged his pointy fingers in his side so he sat up, albeit reluctantly. "No, actually you were pretty good and even made me come. I think you deserve a reward for that.”
In fact, James was supposed to demand for Regulus to get dressed and only show up once Sirius was definitely home too.
He should sink into shame and make a thousand excuses for falling for his best friend's little brother.
But the word reward coming out of Regulus' mouth sounded like the most valuable commodity on earth and James already went this far - if he had to beg Sirius' forgiveness anyway, at least he could get a reward from Regulus. (A stupid idea that unfortunately sounded very good in his horny brain)
Any doubts, however, were brushed aside by Regulus as he unbuttoned James' pants, licked his palm and tucked it under his boxers.
James' cock was only half mast from not paying it any attention, but as soon as Regulus long fingers closed around him, it hardened again.
Regulus moved his hand lazily, tightening his grip only to release it again, drawing circles over James' tip with his thumb.
He was a pure tease, but for some reason James enjoyed it.
James liked it when his toes curled up, thinking he was about to come, only for Regulus to let go and run his fingertips down his length.
James liked Regulus' mean grin.
And James enjoyed the hot kisses Regulus planted down his jaw while all he could do was gasp and plead, knowing Regulus wouldn't listen.
He was even a bit disappointed when he came - panting and moaning in Regulus's hand, who only had his bloody grin on his face - because he didn't want it to be over yet. He wanted to keep kissing Regulus. Wanted to continue to feel his hot breath on the skin. His long fingers on his cock.
But Regulus pulled away, even as he planted one last kiss on James' lips, who sat rasping with the slow realization of what the hell had just happened.
He had given Regulus Black a blow job.
Regulus Black gave him a hand job.
Regulus Black, who was his best friend's little brother. Fuck.
"Don't freak out," Regulus whispered, putting a hand on James' thigh, which freaked James out even more. "Don't worry, I won't tell my brother."
"But I will." James shook his head and scanned his room for his shirt. "I have to tell him."
"It's your funeral," Regulus said lightly, reaching over the edge of the bed for his pants. "But he won't believe that I seduced you. He doesn't think I have anything like that in me.” That was true. To Sirius, Regulus was still the little boy who stuck his nose in books all day and nobody who had sex.
"I owe him the truth."
"Then tell him." Regulus rebuttoned his shirt and ran his fingers through his hair, somehow managing not to look totally fucked. James didn't even dare look in the mirror, knowing full well his lips were swollen and his hair a mess. "But I also have some ideas in case you don't tell him."
This shouldn't sound as interesting as it did. "Oh yes?"
"Yes. I'll let you give me another blowjob.” Regulus planted a kiss on James' jaw and lightly bit into the sensitive skin. James really had to fight himself not to groan. "Maybe I'll sit on your face, too." He licked the tip of James' nose with his tongue and then put his lips to his ear. "And if you're good, you can even fuck me."
"Merlin, the things you're doing to me, Reggie," James gasped, covering his face with his shaking hands. "And if I tell him?" Was there a hint of hope in him? Shame on you James Potter. He could be lucky if Sirius would still talk to him at all – in any case, he would never be near Regulus ever again.
"And he didn’t kill you, you mean? Or neutered?” Regulus cocked his head as if he really needed to consider the question. "Let's see how much I miss you then."
"You're a monster, Regulus, you know that?"
Regulus just laughed, apparently knowing full well. "That was fun. I'll see you tomorrow, Jamie.” He jumped off the bed, slipped on his shoes, and swept his gaze over James one last time, like an artist examining his artwork. "If you live until then."
When Peter came into the apartment an hour later, Regulus was long gone and James had showered, changed the sheets and aired his room, which had smelled of sex and Regulus.
James was wearing a turtleneck even though it was quite warm in their apartment, but he was afraid that if he was wearing a shirt someone would be able to see the numerous love bites on his chest. His fingers were freezing, his heart was beating too fast and James couldn't concentrate on anything, too distracted by the fear that Peter would notice something.
He wasn't a good liar. He never was.
Even as a child, he'd tripped over his words when lying to his parents, and that hadn't changed.
Lying made him nervous and he hated Regulus for putting him in this situation, but he also loved him for giving James what he so desperately wanted.
"Are you okay, Prongs?" Peter finally asked as they sat at the dining table with rice and curry while David Bowie sang in the background. "Did something happen?"
Nothing, just that I gave Padfoot's brothe a blow job, that's all. "No, everything is fine. I just didn't sleep that well.”
Peter nodded, even if he didn't seem to believe him completely. "Moony probably has a calming potion in the bathroom. In case you need something to sleep on?”
"Thank you, Wormy, but I'm fine." He paused and eyed Peter, who was mixing his curry with the rice. He wondered if Peter would be mad at him too if he found out about Regulus. Surely he would be, knowing how hurt Sirius would be by James' selfishness. "You're a good friend, you know. You always try to understand us all, even though we really aren't easy."
"What?" Peter asked confused, his mouth still full of rice. "Are you sure you're okay? Is something up with your parents?”
"No. No.” James chuckled, although he didn't feel like it. "I just had to think about it. I'm glad you're my friend."
Sirius and Remus returned two hours later, quite drunk and quite in love.
James envied the two a little because they managed to remain in love with each other since their fifth year at Hogwarts.
James and Lily had only lasted a year before infatuation faded and turned into friendship.
"Prongs, I'm the happiest man alive." Sirius yelled as he stormed into James' room and threw himself onto the bed next to him (where his brother had been laying a few hours earlier). "Moony jerked me off in the restaurant bathroom and said I could have anything tonight. Merlin, what did I do to deserve him?”
"I don't want to hear about your sex escapades," James moaned, trying not to think about Regulus. That little ass just took up too much room in his fucking brain. "Just use a Silencing Charm, will you?"
"You're just jealous, Prongs, because I have a super hot boyfriend and you don't." Sirius grinned wickedly, which looked so different from Regulus' wicked grin, even though the two were brothers (which James didn't really want to think about). "Don't worry, we'll find someone for you too, okay? No one can resist the charms of James Potter."
And by the looks of it, James Potter couldn't resist the charms of Regulus Black.
James sat up, his hands sweating, but if not now, when else would he tell Sirius.
"Sirius, you know you're my best friend, right?" His heart was pounding so hard in his chest he was afraid it was about to burst out.
"Obviously," Sirius replied, his grin fading and he sat up as well. "Everything okay? Did something happen? Are Monty and Effie alright?”
Now would be the moment, James. Gather your Gryffindor courage and tell your best friend you shagged his brother.
"You're my best friend," James repeated, fingers shaking as he searched for the right words but couldn't find them. "I- I still don't want to have to listen to you and Remus having sex."
Coward. James was a bloody coward.
"Okay mate, don't worry." Sirius laughed again, loud and clear. "I don't want you guys to hear Remus either. The noises he makes are to die for.” He laughed again, getting up from the bed and looking at James again. "You're my best friend too, James. Always have been, always will be."
Fuck, shit. Fucking fuck.
"I know." James tried to smile. He was a coward. "Now go to the love of your life and leave me alone."