Disclaimer: This is a work of fanfiction set in the Harry Potter universe – all recognisable characters and settings are the property of J. K. Rowling and her associates. No copyright infringement is intended. No profit is made from this work. Please observe your local laws with regards to the age-limit and content of this work
Author's Notes: Never written Sirius/James before, so have mercy on me. Thanks to David for the beta read.

Jealousy

Starbursts formed and exploded behind his closed eyes. Holding the pillow tight to his chest, he bit down hard on the corner and tasted cotton, muffling the groan that was wrenched from his lips as he came.

One breath.

Two.

He opened his eyes. James was still sprawled between his legs, head resting on his thigh. His hair was mussed, from sleep and sex, and that grin really shouldn't be legal. Sloppily, James ran the back of his hand over his chin, removing the single, small dribble that had not made its way down his throat. "Good?" he asked innocently.

"Come here," Sirius responded, fingers grasping at him, trying and failing to find purchase on smooth, sweat-slicked skin.

Luckily for him, James was similarly intent on lumbering his way up the other man's body. Awkwardly leaning on his elbows, but with a fair amount of pressure across Sirius' torso, James pressed their lips together in a soppy kiss. Sirius could taste his come on his friend's lips and growled, thrusting his tongue into James' mouth. He loved to kiss like this, sloppy and wet and just a little angry. The girls he had kissed all wanted it to be gentle. No one understood him like James. Threading fingers through the short black hairs at James' nape, Sirius bit hungrily at his lower lip.

"Careful," James gasped, pulling away slightly. His green eyes were bright and wild, offset by perfectly pale skin. "I'm meeting Lily in twenty minutes. She'll know."

And who the fuck cared, Sirius longed to demand. But he wouldn't. Instead, his hand dropped from James' neck, smile falling from his face.

"No puppy dog eyes," James warned him, ducking his head for another kiss. Sirius didn't respond but didn't push James away. "No sulking. You have your girls, and I have mine."

Yes, Sirius had his girls. He had a string of them, a fleet, of pretty girls from the fifth year to the seventh, all quite happy to sneak behind the broom sheds and engage in some extracurricular activities. A different girl every week because it really didn't matter to Sirius which of them he chose, as long as they smiled and they were willing and they blew off some of his excess steam. Excess because James' free time had become somewhat limited. Limited because he had recently acquired a girlfriend.

Sirius had his girls, and James had his girlfriend.

And every time they went out to Hogsmeade together, or took a tour under the Invisibility Cloak, Sirius had a little less time with his friend. His best friend. OK, fine, his fuck buddy.
"Yeah, I know," was all the response Sirius made. There was no point in kicking off. James could be so infuriatingly self-righteous at moments like this. That was the problem with arrogant gits who thought they were right. And why was that such an attractive quality, anyway?
Sirius remembered the first time James had announced – during a blow job, of all times – that Evans had finally, grudgingly agreed to go out with him. He could honestly have bitten it off, so sudden and strong was the rage within him. But he didn't. Instead they argued (and thank Merlin the dormitory was otherwise empty) and then fucked like bunnies on Amortentia. It had been very good sex, and James had collapsed over Sirius' back and laughed and said he loved him. But the hollow feeling inside him hadn't gone away. It was still there the next morning at breakfast, and during Quidditch, and while James and Lily were out, and later when James tiptoed into his bed and spread kisses over his bare shoulder.

It was definitely making its presence known now James was going out on his fourth date that week. What did he see in her, anyway? She was too skinny, had no boobs, and a really annoying laugh. And she was a know-it-all. And she used to be friends with Snape – now, surely, that really was unforgivable?

But apparently not.

"How come you never take me anywhere nice?" Sirius asked, trying to make it sound like a joke. And failing.

"Because we're just friends, right?" James said, not looking at Sirius as he scrabbled amongst the rumpled sheets for his boxers. "We go everywhere together anyway."

They went everywhere together with Mooney and Wormtail, then behind the curtains of Sirius' bed once everyone was asleep, and whispered the most deliciously dirty things. He bet she never did that. He quietly hoped she never would.

"Yeah. You're right," Sirius said. It's the kind of thing he's been saying a lot lately. It's surprising what an otherwise proud man will do for a quiet life.

James pressed another of those wet, searing kisses against Sirius' lips, and his chest burned at the contact of James' hand there. He wanted to pull the other man back down, to wrap his legs around his hips and hold him close and keep him. Instead, Sirius lay there and watched James dress and leave, without any further conversation. They can talk any time. Sirius can only enjoy James' muscles skimming beneath the skin every once in a blue moon.

When James – and it has to be James because everyone else is already asleep – pushed open the dorm door late that night and whispered something inaudible in the dark, Sirius shifted over in the bed. It wouldn't be the first time he'd got all horned up with his new girlfriend and came back to Sirius to finish the job properly.

Then there was a giggle, a hideously familiar female giggle, and Sirius had to swallow down the urge to throw up. Lying very still and breathing shallowly, he tried to convince himself, as much as anyone else in the room, that he was asleep. Eyes closed tight, he could almost see them writhing together in the darkness. She let out little breathy gasps, and Sirius was certain he wasn't the only person hearing this. He's kept quiet for years. Evans was such a novice. But these seem to have some odd effect on James because he's muttering things to her, too; he was groaning and sighing in ways Sirius couldn't have imagined in his dirtiest, most illicit fantasies.

He didn't know when he's fallen asleep, but at some point he did. The sunlight woke him in the morning. He sat up in his bed and looked around. Lily had gone, but her presence was still there. It smelled of her, and it was disgusting. When James sat up, Sirius cowled at him.

James just smiled.

Bastard.