@microcest / @macrocest prompt: “that isn’t mine” / 621 words / tw incest duh
also added to ao3 here
“What is…” Sirius slid his leg back and forth between his sheets again, his foot catching on a stray piece of fabric again. He hooked it over his toes before dragging it up to the opening and transferring it to his hand.
It was a pair of boxer briefs, green with a grey waistband, and definitely not Sirius’.
“Regulus!” Sirius called, not wanting to get out of bed, and knowing his younger brother was still awake in his own bedroom. “Reggie, come here!”
“What?” Regulus asked as he stepped into the doorway, expression and tone equally bored. He was dressed in nothing but a pair of pajama pants, a book in his hand with his index finger squished between the pages to hold his place.
“Why are your underwear in here?” Sirius asked, holding up the offending article of clothing to show Regulus. There was a damp spot at the front, dark and stiffening, as if Regulus’ cock had been leaking at the tip before he finally kicked them off, like maybe… “Did you fuck someone in my bed?”
Sirius willed his heart rate not to spike at the visual, silently begging his own dick not to grow hard at the thought of his brother writhing around in the exact spot he was currently laying in.
A blush crept up Regulus’ cheeks at the accusation, but he shook his head all the same. “No, Sirius,” he said, tone suddenly patronizing. “I didn’t fuck someone in your bed.”
Sirius looked at the underwear in his hand, thought about the way they had so clearly been pushed off under the covers in a fit of rushed desperation, and wondered if Regulus had left them for Sirius to find, or if he had simply forgotten them.
“Did you—” Sirius felt his voice break and paused to take a deep breath to steel himself. “Did you jerk off in my bed, Reggie?”
Regulus let out a soft, embarrassed laugh, looking away from Sirius’ gaze. “Of course not, Sirius.” The words were soft, devoid of emotion, and clearly a lie. Regulus wasn’t trying very hard to hide the truth of what he had done.
“Why in my bed?”
“It smells like you,” Regulus replied, his blush spreading further down his face and across his bare chest, but there had been no hesitation in the words.
Oh fuck.
Sirius clenched his eyes shut and dragged in another deep breath. His heart was racing, even as he felt all of his blood rush to his cock at the insinuation.
“You think about me while you touch yourself?” Sirius asked, opening his eyes to look back up at Regulus. He knew his own pupils would be blown wide, lust-crazed and desperate, but it was Regulus that had started this. It was Regulus’ desperation that had led Sirius to realize the thrumming need under the surface of his skin, and Sirius knew Regulus wouldn’t reject him.
Regulus sucked his bottom lip into his mouth and nodded his head. “I can only come when I’m in your bed.”
Regulus could only finish when he felt close to Sirius, when he was surrounded by his scent and his belongings? What would Regulus’ orgasm be like if he came with Sirius in the bed with him?
“Show me,” Sirius said, tossing the underwear to the side and scooting over to make room for his brother. “I want to see your pretty face when you come on my sheets.”
Regulus’ breath audibly hitched. He tossed his book onto Sirius’ dresser before stepping further into the room, all bashfulness just as forgotten as the page he had been reading.
Regulus grinned, a sultry, sexy thing, before sliding his pajama pants down his legs and kicking them off to the side.
“Make me, Siri.”