It should have been more disturbing to see his younger brother on his knees and going at Remus like that, disturbing to see how much Remus was enjoying the attention, but the pleased noises Regulus was making and the look of bliss on Remus's face—there was nothing disturbing about that. Remus untangled one hand from Regulus's hair and held it out to Sirius, a sign Sirius had never been able to resist.
"Different," Sirius commented before taking the proffered hand.
"He's good," Remus said with a grunt. "You want him after?"
Regulus made a small noise of protest, but Remus held him firm, not letting his reactions sully the moment.
"You're overdressed." Remus knotted his hand in Sirius's tie, pulling Sirius into a kiss.
"I'm also late and extremely aroused, but we needn't go on stating the obvious." Sirius grinned into the next kiss, pleased when Remus let go of his tie and started working on the buttons. He undid his trousers while Remus kept opening up his shirt.
"You two talk a lot," Regulus protested, coming up for air. He wiped his red mouth on his wrist. "It's a wonder you ever get to fucking."
Sirius rolled his eyes. "Shut it, would you?" Sirius bit back the rest of his taunts, a promise he made to Remus so that this would happen, so that Remus would forgive him.
Quickly divested of his clothing, he moved behind Remus, doing exactly as Remus had asked. He prepped Remus slowly, kissing his neck and biting his shoulders, murmuring words he hoped his brother didn't quite hear. He stayed as much behind Remus as possible, still not sure that he wanted to watch his brother suck off his boyfriend—but he couldn't complain with the way Remus was moaning and panting, demanding more, demanding. . . .
"Padfoot, get on with it!"
With a slight smirk, Sirius removed his fingers, lining his cock up and kissing Moony's neck. "I'm sorry," he whispered as he pushed in slowly, making small movements until he was completely sheathed. His eyelids fluttered as he listened to Remus's contented sigh.
He pulled out slowly, enjoying the friction, and then pushed in hard, earning a grunt from Remus and a snort from Regulus.
Remus's hand reached back, pulling Sirius's head forward, patting awkwardly. "Good, good." Regulus made a loud wet noise, and Remus lost control of his syllables, his words spooling out into moans.
Peering over Remus's shoulder, he watched Regulus work Remus's prick, giving Sirius a fairly good idea of what he usually looked like. He was suddenly aware that from this angle it was almost like Regulus was sucking off him, like he was opening his arrogant little mouth for Sirius and hungrily taking in his brother's prick.
Fast slapping sounds penetrated his ears as he realized Regulus was pumping his own dick. The beat was familiar, sounds Sirius had only ever before heard through a closed door. Sounds Sirius had always pretended he didn't hear and didn't make him aroused.
"Uh," Remus grunted, pulling Sirius's arm around his chest, and Sirius understood it to mean, "Get on with it." So, Sirius thrust, giving Remus a real reason to moan, writhe, and buck into Regulus's warm, waiting mouth.
He ran his hands over Remus's chest, down to his waist, thrusting and forgetting about anything other than Remus. Remus's skin was smooth beneath his fingers, marked with only a few scars. Running his fingers lower, he bumped into a thin hand—not Remus, Regulus—and jerked. But Regulus reached for him, pressing his hand against Remus's flesh, Regulus slipping his fingers into Sirius's palm. Sirius bucked his hips, pushing Remus deeper in Regulus's mouth, and his brother took it, rising up with the motion like he knew what Sirius would do.
He soon couldn't control his own noises, groaning and whimpering his pleasure, telling Remus all the things he wanted to do to him, in him, with him. Regulus squeezed his hand, finally letting go. His hips snapped up into Remus with abandon, his cock aching with need until he felt Remus clench, his body going rigid in Sirius's arms, and, with Regulus's coughs as the background music, Sirius felt himself pulled into Remus as they shared their orgasm.
He felt himself coming down slowly, only now aware that he'd breathed a name into Remus's ear when he came. He swallowed hard, glancing from the corner of his eyes, but Remus was looking down, petting Regulus's hair as Regulus licked Remus clean.
"He's such a good boy," Remus said, a small smile on his face. "I think we should keep him."
Regulus sat up, the familiar Black scowl on his face. "This was a one-time deal, Lupin. In exchange for," Regulus motioned with his hand, and finally Sirius saw the photographs next to Remus's shirt. He couldn't make them all out—some were upside-down or partially covered—but Regulus was definitely in a few, naked and enjoying himself . . . with several different partners.
"Of course." Remus leaned over slightly, Sirius's softening prick sliding out. He handed over the photos with no preamble. "I appreciate you humoring me."
Regulus flipped through the photos, smiling at a few. "It wasn't entirely appalling. Despite the sentimental declarations." Sirius growled, not sure if he was more mad at himself for speaking to Remus as he normally would, or mad at Regulus for being an insufferable prick.
He tucked the photos into a pocket in his robes, shrugging the garment over his shoulders. "Besides. . . ." Regulus leaned in, his face coming over Remus's shoulder. "I like hearing people call my name." He kissed Sirius hard, tongue sliding past Sirius's lips, and Sirius couldn't remember the last time he'd been kissed by someone other than Remus. Definitely couldn't remember the last time he'd been kissed this good or deep. Sirius tilted his head, expecting it to go on, but Regulus pulled away, licking away Sirius's saliva. "Brother." He picked up his clothes and left, not turning around again.
"Now that wasn't so hard was it?" Remus said, turning and facing Sirius. He cupped Sirius' cheek, pulling Sirius into a familiar, welcome, and less frustrating kiss.
Sirius scratched his brow, not quite sure what to say. He'd kissed his brother, said his name while. . . .
"You seemed to enjoy it at least . . . more than you thought you would." Remus laid Sirius's tie around his neck and pulled over his own shirt.
"Remus, I. . . ."
Remus laid a finger on Sirius's lips. "Next time it shouldn't be for an apology." He pulled on his shirt, cocking his head to the side in thought. "And next time, I think I want him to fuck you."
Sirius swallowed hard, more confused than he was when he had first entered the room. It was one thing for Remus to ask to fulfill a fantasy, but entirely more disturbing was that Remus even knew about Sirius's fantasy.