"You know me best too," Sirius admitted softly, mirroring Remus' posture unconciously. He loved James deeply and completely, but Remus had always been different. Remus understood, in ways James never could. Because James had grown up happy. Sirius had told Remus things he'd never told anyone else. Remus knew about the dark thoughts, and about how completely Sirius sometimes believed them. Remus was the first person Sirius went to when he was afraid, or lost. Remus never needed him to say anything, he just got it. Sirius would miss that the most.
The word pack brought out a small, true smile from Sirius. It was the one thing he hasn't thought of, and that could never truly be taken away from them. Moony and Padfoot. Sirius would have done anything, anything at all to stop his friends pain. He would never forget sneaking into the Hospital wing to see him first year. The wounds, the hurt, he would carry that in his heart forever, and he'd decided right in that moment that he would find a way to make sure Remus never had to be alone as the wolf again. That memory was inextricably linked to the one where they showed Remus they'd done it. They'd become Animagus, and they could be with him for every moon for the rest of his life. That hadn't happened, he knew now, but Padfoot would never willingly leave Moony alone again. No matter what distance there was between them, they could still run on the full moon.
"Padfoot will run with Moony until the world ends," Sirius said, still smiling. His eyes were wet, and his throat was closed, but the smile was real and he was keeping it.
"I'll talk to him," Sirius agreed. What else could he say? He wanted them to be happy, to be able to move on, and they couldn't if this thing between Reg and Sirius stayed the same. So he'd tell his brother how happy he was, and apologize for being shitty, and offer to be there if his brother needed him. Everything else he'd just lock away again. Peter was wrong, talking about it wouldn't help any of them.