Disclaimer: JK Rowling owns the HP universe and its characters

"I don't know why you even bother with him," James said, passing the quaffle back to Sirius. They were sitting on their beds, blowing off steam after yet another public argument with Regulus by tossing the quaffle between them. Remus and Peter were in the Common Room working on the Potions essay Slughorn had set to give Sirius a bit of room to calm down. They all knew that Sirius had a hard time thinking straight when he was angry or exasperated.

On the contrary, Sirius felt that he was thinking as clearly as ever. Sighing, he said, "He's my brother, Prongs." James nodded, deftly catching the ball, but Sirius knew he didn't really understand. And how could he? He was an only child. Remus and Peter were, too. None of them could fathom the connection between siblings. They couldn't imagine that feeling of a common history, a basic understanding of your childhood and the events that shaped your personality, the disappointment when your brother falls in with the wrong crowd, the heartache when he claims he hates you, or how you could love him so much anyway, after everything. Sirius didn't quite understand it himself; sometimes he wished he could turn off his feelings so he could easily break ties with Regulus, but that would be the Black thing to do, and Sirius would not become like them. The other Marauders couldn't understand why Sirius fought so hard to save Regulus from his inevitable path. In their eyes, he was a lost cause, just another Slytherin.

But Sirius knew differently. Both Andromeda and his Uncle Alphard had been in Slytherin, and they'd turned out fine. And Sirius could see that Regulus wasn't as far gone as other Slytherins; he was just a good actor. Regulus knew how he needed to act, and so he did. He didn't want to get in trouble—he especially didn't want to be punished in the same manner as Sirius was—and so he became everything his family and housemates wanted him to be.

When Sirius was punished at home, however, Regulus always made sure he was alright afterward. He'd sneak into Sirius' room after their parents and Kreacher had gone to bed, and help tend to Sirius' injuries. He washed off blood, bandaged cuts, applied salve to bruises, and helped his brother into bed. When Sirius was sentenced to his room without dinner, usually several days in a row, Regulus would slip him leftovers late at night or early in the morning. When Sirius was locked in the closet or basement for hours, Regulus—who, unlike his brother, was permitted possession of his wand over the holidays—would send a small light under the door to accompany Sirius in the darkness. Sirius refused to believe these were the actions of a future Death Eather.

"Wotcher!" Sirius startled out of his reverie, just in time to catch the quaffle a millimeter from his face. James rubbed the back of his neck sheepishly. "Sorry, mate."

Sirius shook his head. "No, it was my fault. I kind of spaced out for a minute there."

They continued to pass the quaffle back and forth, now in silence. Sirius was doing his best to clear his mind of anything related to Regulus. It hurt too much sometimes. He was a good kid, really he was, and Sirius couldn't stand by idly to let him become everything their parents were. "Hey, Sirius?" James began, breaking the silence. "Can I ask you a question?"

"Sure, shoot."

James caught the quaffle and held onto it, forcing Sirius to shift his full concentration to him. "You have to…just promise you won't get angry," James said tentatively.

Sirius blinked. "Okay," he agreed warily, drawing out the word.

James took a deep breath, picking at the leather seam of the quaffle. "We're brothers, right?"

Sirius didn't need to hear any more. "James," he growled dangerously. James visibly gulped; it was never a good sign when Sirius used his given name, especially in that tone. "You cannot be that self-centered."

"I didn't mean—" James started, but Sirius interrupted him.

"Yes, yes you did mean it like that!" Sirius insisted, voice rising. "You were implying that you are more important to me than Regulus!" James flushed and tried to defend himself, but Sirius pushed through. "To answer your question, James, yes: you are my brother by choice. But do not make the mistake of thinking that means I love you more than Regulus. I don't. And I don't love him any more than you."

"Yeah, well, some days it seems like it," James mumbled. His neck reddened in shame immediately. He knew he shouldn't have said it, but he truly felt like Sirius was ignoring him for his stupid Death Eater wannabe brother lately.

Sirius grew quiet, uncomfortably calm. "So there it is. You're jealous." It was a statement—a cold, hard fact—not a question. James couldn't meet his friend's eyes. "Look, Prongs, if your situations were reversed—if Regulus was completely safe and you were in danger of potentially joining the Death Eaters—you know I'd be acting the exact same way about you. But you're the safe one. And thank Merlin for that. Because I still need you. I need your help."

James looked up to meet Sirius' gaze. His face was solemn and tired. James could see the bags under his eyes. "Regulus won't listen to me any more than you," he pointed out.

Sirius shook his head, blinking heavily. "That's not what I meant. I need you to keep me together. This shit keeps me up at night. I'm too nauseous to eat. I keep forgetting things. The point is, I can't help Reg if I'm falling apart. But I don't know how to fix it."

James smirked slightly, understanding finally washing over him. "No, you never have been very good at taking care of yourself when you're worried about someone else. I mean, Merlin, look at your hair!" he jibed, throwing the quaffle at his friend so fast it hit Sirius in the head, mussing up his prided black locks.

Sirius smoothed down his hair, glaring at James but grinning easily. "Stuff it, Potter." He wanted to say more, to thank James, but he knew James would just call him a poufter and brush it off. And anyway, he knew James understood. Now if only he could make Regulus understand.