Chapter Text
When Regulus was born, Sirius was only five, but he immediately took responsibility for his baby sibling. He checked on Regulus every time he cried—more often than his parents did—helped him learn how to walk, taught him how to read. Sirius was the person Regulus went to every time he needed support or had a question or just wanted a hug. Sirius was the first person Regulus told when he was able to put his feelings about his body into words. When he knew how to ask that people used different pronouns for him, it was Sirius he asked first. It was always Sirius and Regulus, together, against the world, even ten years later.
It shouldn’t have been a surprise then that Regulus came to Sirius first with this newest problem.
“Sirius?”
Regulus stood there in his doorway wearing one of Sirius’ t-shirts. It was practically a dress on him, but he didn’t seem to mind. He also didn’t seem to be wearing anything else and his long, gangly legs were bare, poking out from beneath the hem.
“Yeah, Reg?”
“I need your help with something… personal.”
Embarrassing, Sirius corrected inwardly.
“Yeah. Sure. Come into my office,” he said gesturing around at the mess that was his bedroom.
Regulus came in and shut the door. He played with the edge of the shirt, lifting it just a little too high. High enough that Sirius could see the way he wasn’t wearing any underwear. Sirius cleared his throat and looked away, but Regulus didn’t seem to notice.
“I… it’s really embarrassing.”
“You can tell me.”
Sirius patted the bed beside him and Regulus sat down. His shirt rolled up a little so his bare ass was sitting on the sheets and Sirius tried hard not to think about that. He didn’t succeed, but he tried.
“What’s up?”
“It’s… I was laying in bed and my—between my legs—started getting all—“
Sirius was holding his breath, but Regulus didn’t seem to be able to finish the sentence, so he said quietly, “Wet?”
Regulus nodded, face flushing furiously. “I don’t know if something’s wrong with me and I don’t know who else to ask.”
“Oh, Regulus,” Sirius said gently. He put a hand on Regulus’ bare knee. “There is nothing wrong with you.” He meant it to be all-encompassing and Regulus seemed to understand that.
“Can you look? Just to make sure.”
“No, I can’t— that’s not— it’s private, Reg.”
“Please? I can’t ask anyone else.” There was something unspoken there. Something about not wanting anyone else to see him there, not just because he was embarrassed or because it was private. But because he felt wrong between his legs. “I trust you.”
You know me. You know who I am beneath the skin. That’s what he’s saying.
So Sirius said, “Fine. Lie back and open your legs.”
Legs frogged out, shirt up around his waist, it was impossible not to look at him now. There in between his legs, he was pretty and pink and, yes, very wet. Sirius reached out his hand, then dropped it to his side. Look, don’t touch.
Still, he knelt beside the bed. Just to look. Just look.
“What were you thinking about? When you noticed it, I mean.”
“You,” Regulus said. So fucking innocent. “I was thinking about… Remember the other day when I came in and you were getting dressed? I was thinking about that. And then I got like this.” He gestured between his legs.
“What do you know about sex, Reg?”
“Enough.”
Doubt it. “When you’re… When you’re aroused, you get like this. Wet. It’s normal.”
“Aroused?”
“Horny.”
The temptation was so impossible. Regulus didn’t move, even with his questions answered, and Sirius could only imagine sinking himself inside there and reveling in the heat. He resisted though.
He did, however, put his hands on Regulus' inner thighs, then pressed his thumbs against the soft lips and pulled them apart. Just to see.
“Sirius?”
“Just looking.” Sirius could feel his mouth watering and the smell was intoxicating.
“Is it okay?”
“Perfect,” he breathed. He blew air on it and it twitched. “Fuck.”
“What?”
“Nothing just… nothing.” His thumbs were still holding the lips open and he let one of them stray a little closer to the center. “Have you ever touched yourself here?”
“Yeah, but it just feels wrong. I wish…”
He didn’t have to finish the sentence. Sirius knew what he wished.
“You can pretend, you know. It’s not the same, but you can pretend it’s how you wish it was. Imagine.”
“Like how?”
Sirius breathed out a shaky breath and pulled his hands away. “I don’t think we should be doing this.”
“No one else will talk to me about this, Siri. Please.”
It was true. Sirius knew it. Their parents were still trying to pretend that Regulus was their perfect little daughter. They pretended not to see the way he was struggling. The way he needed support, not suppression. Where else was he supposed to go? The internet? Sirius would prefer his brother came to him first.
“Fine,” Sirius said finally and pretended it was just because his brother needed help. Not because he also wanted to touch, not just look. “Can I touch you? I want to show you what I mean.”
“Yeah,” Regulus said, sounding uncertain. But he was always trying to keep up with Sirius. He wouldn’t turn down the chance to do something grown up together.
All he’d done was look so far, but Sirius could feel the significance of this moment. They could turn back right now. He could turn back. But fuck, Regulus was so gorgeous and willing and wanting. Sirius never could resist giving him what he asked for.
Sirius let his fingers trail over Regulus’ inner thigh, leaving goosebumps there, and then let his hand rest on Regulus’ center. It was so wet, but Sirius reached for the nub there, pinching it gently between his fingers, then rubbing gently.
Regulus convulsed, his whole body spasming.
“Wait! Siri, that’s—“
“That’s what it’s like to have your cock stroked. Close your eyes.” Regulus did and Sirius started massaging the little nub until Regulus was breathing hard. “That’s what it feels like. You like it when I rub your dick?”
“Yes,” Regulus whimpered. “Feels so good.” His hips were twisting, like he was trying to get away from the good feeling and also maybe feel it more.
“And you imagine that this finger is going into your ass,” Sirius said and slid just the very tip of his finger into Regulus’ warm, wet center.
“You could just put it in my ass,” Regulus suggested, breathless.
“No. You’re still too small back there, Reg. Someday you can, but for now we just pretend.” We pretend. He’d gone so dangerously far—maybe past the point of rationality— but he couldn’t stop either. They were just pretending, right?
“I’m not small there?” Regulus asked. His legs were shaking and he was grasping at the sheets.
“Not as small. I’ve got my finger in, don’t I? So pretend for me, Reggie. What am I doing?”
His voice trembled when he said, “You’re rubbing my cock.”
“Where’s my finger?” Sirius asked.
“My—my asshole.”
Fuck it sounded so pretty when he said it.
“Such a big boy. You’re so grown up.”
“More,” Regulus croaked. “I need more.”
“I don’t want to hurt you.”
“Just put it all the way in.” Regulus’ hips lifted from the bed for a moment, then dropped back down. “Please.”
Sirius pressed in. There was no real resistance, no noticeable hymen, but Sirius wasn’t surprised. Regulus had said he’d touched himself down here before. It was so tight around his finger and he couldn’t help but think about the way it would squeeze his cock if only he could slide himself in, press forward until Regulus was twitched around him the way he was right now.
He started the slow stroke in and out with his finger that mirrored the stroking of the little nub at the top, starting a rhythm that had Regulus whimpering in no time. Sirius squeezed his own thighs together, welcoming the pressure and already feeling guilty for wanting more of it.
"What's—Something's happening, I don't—"
"You're gonna come, Reg. Relax, you're doing so good."
Regulus whined a high pitched sound and his thighs clamped around Sirius' hand. A flood of liquid gushed from him over Sirius' fingers, leaving them sticky and wet and smelling like Regulus.
Sirius dropped his hands away from his brother and crumpled forward. He didn’t touch himself, as badly as he wanted to, because he was afraid that if he did he wouldn’t be able to stop. That he’d sink himself inside his brother without a second thought.
“Sirius?”
It was only the sound of Regulus’ voice that could make him straighten up just then.
“Was that good, Regulus?”
“Yeah. It was.” He propped himself up on the bed on his elbows, looking down at Sirius, still exposed, legs apart. “Are you okay?”
“Of course. I’m great.” Too good. “You should go back to your room. Before anyone finds us like this.”
“Yeah. ‘Course.” He hopped off the bed, shirt falling to cover him even though modesty couldn’t possibly fucking matter between them anymore. He turned back at the door, hand on the knob, and said, “Thanks, Siri.”
He left and Sirius locked the door behind him, flopped down on the bed and pulled his cock out. Hand still wet with Regulus’ juices, he rubbed it along his cock, closed his eyes and pretended it was Regulus. It took him no time at all to come.
For two weeks, they pretended like nothing had happened. It was always there in the back of Sirius’ mind, but he said nothing about it.
And then, at midnight one night, there was a soft knock on his door. No one ever knocked on his door but Regulus. He turned the music pulsing from his speakers to a low hum, background noise, then got out of bed and cracked the door.
“What, Regulus?” he asked before he even really saw his brother. But there he was, wearing only that shirt. The same shirt. “Fuck, Reg, go back to bed.”
“I can’t.” Regulus bit his lip and looked away, flushed cheeks and sweat on his brow.
“What do you need?”
Very low, quiet, Regulus said, “I need you to touch me again.”
Sirius shut the door.
Regulus, of course, knocked again and Sirius had to open it. He couldn’t just leave his brother standing out there.
“I’m not doing it again,” he said.
“I’m so wet,” Regulus said and Sirius nearly folded right then and there.
“It’s not—It’s not a thing a brother should do for you.”
“Please, Sirius,” he whined, pained. Like it was hurting him to be so aroused.
“Do it yourself, Reg.”
“I tried to do it on my own and I couldn’t—”
“Couldn’t come?”
“Yeah. Please?”
Fuck, it was all so fucked up. But Regulus looked like he was right on the edge of tears.
I want to make him cry.
Fuck, stop. Don’t think that about your brother. God.
“Okay, fine. I’m not touching you though.”
Regulus came the rest of the way in and laid down on the bed. “What are you going to do?”
Sirius locked the door. “I’m going to help you touch yourself.”
Regulus swallowed and nodded. He looked so little there, raising his hips up to slip off his underwear. They were absolutely soaked and Sirius had to look away for a moment to try to get himself under control. But when he looked back Regulus was all splayed out again, fingers over his center and Sirius didn’t think he could gain control of anything just then. The momentum they had was propelling them forward at blinding speeds and he was now only along for the ride.
Sirius got between Regulus’ open legs, pictured himself pushing his already-hard cock inside, then shook his head and knelt there instead. “Show me,” he croaked. “Show me what you were doing.”
Regulus slid tentative fingers between his lips, careful and nervous and jerky in his gentle ministrations.
“A little more pressure. Not too much.” Sirius put his hand over Regulus’, and put a little more pressure there, which made Regulus gasp.
“Yeah. That’s good.”
For a while, they rubbed like this with Sirius helping Regulus move his hand just right.
“The angle,” Sirius finally said. “It’s a bad angle for me. Let me get behind you.”
Regulus nodded and sat up, never taking his fingers away from his center. Sirius got behind him and he laid back against Sirius’ chest. He fit so perfectly there between Sirius’ legs, in his arms, that it was hard to ignore the hardness in his own pants.
Fuck it, Sirius thought and slipped his cock out so that it was slipping up beneath Regulus’ shirt, up the soft skin of his back. Regulus pushed back into it knowingly.
“I’m just helping, okay? Not touching, just helping.” He said it more for himself than for Regulus.
“I’m so hot,” Regulus complained, letting his head loll against Sirius’ chest.
“I know, I know. I’m going to help.”
Sirius put his hands flat on Regulus’ stomach and groaned at the way his skin felt. The slide of it against his own as his hands wandered lower. Down between his brother’s legs. He stopped with his hands over Regulus’ so he wasn’t really touching. Regulus was touching himself, Sirius was just adding pressure.
“Like this,” Sirius said and started swirling his fingers in long circles so Regulus’ fingers were rubbing over his nub. “And you can press a finger inside like this.”
Sirius pushed against one of his brother’s fingers, so it slid in. Sirius’ finger followed.
“It’s so good when you do it, Siri.”
“You’re the one who’s doing it,” Sirius whispered in his ear, but he relished the feeling of Regulus’ heat around his finger. He thrust his hips in long, slow strokes against Regulus’ back. The longer he did it, the more he lost himself to the pleasure of it. The more he rubbed Regulus, rather than helping Regulus rub himself.
He didn’t notice until later that Regulus took his hand away. Sirius’ hand was the only one on his hole, dipping into it, his palming pressed against the nub. Regulus writhed against him, toes curling, nails digging into Sirius’ thighs.
“I’m so close.”
“Come, Reg. Come on my fingers like a good boy.”
That sent him over the edge. His hole tightened around Sirius’ fingers and the pulsing of it pulled Sirius over with him. He wrapped his free arm around Regulus’ waist and pulled him in tight as he came, sticky spurts up his t-shirt.
“Fuck,” Sirius groaned.
He held Regulus like that for hours, long after the pleasure had subsided.
“Thank you,” Regulus murmured, sleepy now against Sirius, the only thing between them Sirius’ come.
“I love you, Reggie. I’d do anything for you.”
“I know.”
Sirius knew he should discourage it, but it became routine. When Regulus was wanting and wet, he came to Sirius’ room and they got off together.
Worse than that, they kept pushing the boundaries further. Hands, mouths, exploring, touching. Soon Regulus was asking for more.
“Can we just rub them together? Not inside, I just want to know what it feels like,” he said late one night.
And Sirius never could resist him.
He sat back against the headboard and Regulus climbed into his lap, straddling him like it was second nature. He hovered just enough that they weren’t touching there, where the searing heat between their legs was almost painful with need.
“Just enough to make you come, okay Regulus?”
Regulus nodded and lowered himself until Sirius’ cock was slipping between his lips, pressing up against that little nub, but not pressing inside of him. “It’s hot, Siri. Your—your cock.”
“Yours is too. So hot, burning me up,” Sirius moaned.
The contact was enough to keep him hard, but he needed friction to get further. Regulus provided it. He rolled his hips—like he’s fucking made for it—rubbing the length of his hole up and down Sirius’ cock. He left a trail of wet along the underside of Sirius’ cock and the slick motion was definitely going to make him come.
“You getting there, Reg?” Sirius asked, because his brother’s face was contorted in concentration.
“Yes, but it’s not enough.”
Greedy, aren’t you?
“What do you need?”
“I don’t know,” he whined, starting to sound desperate. “Help.”
I could put it in you. “I’ll try,” he said instead.
He grabbed Regulus by the hips and pulled him down with each roll of the hips, adding pressure, making the friction almost unbearable in its enhancement.
“Fuck, Reg, I’m getting close.”
“I’m not,” Regulus whined. He looked like he might cry, tears welling in his eyes he needed it so badly.
“Okay, okay,” Sirius said. He slipped his hand between them and stuck two fingers up into his brother. They slid in so easily with how wet he was, how open.
Regulus moaned and seemed satisfied with this. “Right there, Sirius. That spot—it’s something different. Good. So good.”
Sirius kept pressing down with one hand, sliding the other fingers into him and they were both moaning too loud and breathing hard.
“Something’s going to—I’m going to pee or—”
“You’re going to come, Reg.”
“But—”
“Just trust me. Come on me,” Sirius said.
Regulus fell forward, flinging his arms around Sirius’ shoulders, crying out as he squirted all over Sirius’ lap. Sirius pulled his fingers free and stroked his cock, pressing the tip perilously against Regulus’ opening. So fucking close. But he stopped himself right at the entrance, tip pressed there as Sirius came.
“Fuck,” he groaned as his come filled his brother. “Fuck, I’m sorry, Reg.”
“No, it’s so good,” Regulus murmured into his shoulder.
Afterward, they cuddled for a long while. Sirius almost let the guilt choke him, certain that in his silence Regulus was hating him.
But he turned to look at Sirius eventually and asked, out of nowhere, “Is something wrong with me?”
Sirius stroked his cheek, gently. “Why would you ask that? There’s nothing wrong with you.”
They were fully facing each other now and Regulus whispered, “Why do I feel so wrong, then?”
“I’m so sorry—”
“Not like that.” Sirius let his forehead fall against Regulus’ as Regulus explained. “This—what we’re doing—”
“We shouldn’t be doing it.”
“Would you shut up for once in your life and let me finish a sentence?” Regulus snapped. Sirius clamped his lips shut tight and Regulus sighed. “When we do these things, I almost feel normal. Like I’m seeing myself how you see me. But the rest of the time, my body feels so wrong.”
“This helps?”
“Temporarily.”
How could he say they needed to stop now? He couldn’t, not when his brother had finally found comfort somewhere.
“That’s not your fault. There’s nothing wrong with you. You’re perfect.” He kissed Regulus on the forehead. “I love you.”
“I love you too, Siri.”
Regulus didn’t only come to Sirius when he was horny. He did when he was scared too, and Regulus was scared of nothing more than he was of storms.
The moment Sirius heard thunder that night, he knew. He wasn’t surprised when Regulus was cracking his door open.
“Can I sleep in here tonight?”
Sirius moved over and made space, held the blanket up so Regulus could slot in beside him. He slid in, back to Sirius’ chest, and Sirius wrapped an arm over Regulus.
“Some day you’re going to have to figure out how to sleep alone during a thunderstorm.”
“Not while you’re here,” Regulus said brightly and cuddled back into Sirius. His ass wiggled and Sirius swallowed. It was pressed right into his crotch and the friction was impossible to ignore.
“Alright, go to sleep,” Sirius grumbled.
They lay there in silence for a long while, but every once in a while Regulus would press his ass backward and Sirius would try not to groan and thrust his hips forward. For a long time, Sirius thought he was doing it by accident. It became obvious that this was untrue when Regulus’ hand snaked back between them and squeezed the bulge on the front of Sirius’ sweatpants.
“Hey!” Sirius snapped, jerking his hips back even though this was exactly what he wanted.
“You’re the one who’s hard,” Regulus retorted and squeezed again.
“I can’t help it. You keep wiggling your ass and you’re so fucking warm.” So hot.
“I can make you come. You know, just so we can sleep.”
“Oh, that’s the only reason why?” Sirius asked.
“Isn’t that what you want?” Regulus asked. His hand slid beneath Sirius’ waistband and he pulled out Sirius’ cock.
“Yes,” Sirius said, voice small and shaky.
Regulus put Sirius’ cock between his thighs so that with each thrust it prodded his nub, his hole. Sirius couldn’t help but thrust. Regulus’ thighs were soft and warm and smooth.
But Regulus was moving his hips too, in a way that was adjusting the angle of his cock. Changing the angle so that it was pressing against Regulus’ entrance. Sirius tried very hard not to thrust. But he did. Just a little. And the very tip of his cock, slipped just past the entrance. They both froze.
“Sirius,” Regulus breathed.
“Yeah?”
“You’re inside me.” He didn’t sound upset or scared or angry. He sounded glad.
“Barely. I can pull out.” There’s still time. We can still stop this.
“I don’t want you to.” Regulus was the one to press back, but he yelped at the first twinge of pain and stopped.
“You’re too young. It’s going to hurt.” Sirius rubbed his back gently and he relaxed a little.
Regulus whimpered. “I want to do it, Sirius. With you. Put it in my ass, please.”
“Fuck, Reg. You don’t—you don’t understand what we’re doing here. You’re too young for this.”
It was true. So obviously true. They might both be kids, but Regulus was a child. A five year age gap was too much, too far. Sirius knew it. He knew he was doing something terrible but god fucking damn it, it felt so good.
Sirius pulled back, afraid, guilty, but Regulus pushed against him, panting against the pain and soon he’d slid all the way down Sirius’ cock.
“Regulus—”
“Don’t. It’s done. Might as well finish, right?”
Sirius kissed the back of his neck. “You’re so stubborn.”
“It’s one of my only talents.” He rocked gently so that the in and out of Sirius’ cock made them both whine. “Come on, Sirius.”
And Sirius never could resist his brother.
“I can’t— I won’t last long, Reggie, your hole’s so tight and hot. Fuck,” Sirius groaned. He was already holding back, hoping to get Regulus off too, but he didn’t think that was going to happen.
Regulus dipped fingers between his legs, rubbing himself. “I’m getting there. I’m close,” he whimpered.
“Come on me. Good boy, Reg, come on me now.”
Regulus made a sound in his throat, something deep and guttural and wanting. And he rolled his hips as his hole tightened, pulling Sirius with him over the edge of their shared orgasm.
“Fuck, fuck,” Sirius whined as he shot come in his little brother. “So good.”
Regulus grabbed back at Sirius’ hips, orgasm going on for long enough that he was still in the last of it when Sirius was done.
“You can always come to me,” Sirius croaked. “For anything.”
“I know, Siri. I always will.”