Remus was aware there was still a distance between them. But, he wasn't sure if that was still Sirius trying to shut him out or Sirius' needing some space from Remus, who was well aware that he was likely breaking his best friend's heart. To make it a little less awkward, he twisted on the sofa and pulled one leg up so he could rest his chin on top, arms looped loosely around it.
"I'm always going to need you," he said with a smile. "You're my best friend. You know me better than anyone, even James and Peter. I told Peter that none of you comes first above the others, that I can love each of you equally, if in different ways. And that's true. But, you've always been the one I feel closest to. You're pack, Pads." That really said it all as far as Remus was concerned. Pack was family, the closest thing Remus had left. Unlike James and Sirius, the castle had taken his blood family back. His friends were what he had left. Now there was Regulus and he was special. But, it was also new and it wasn't practical to think that they would be forever. Regulus was only nineteen. Eventually, he might move on; they could decide they made better friends; the castle could take any of them at any time.
"I'm going to try not to get between you two, or push you too much. But, out of all the people the castle could have brought back, you two got lucky and have each other back. And, selfishly, I care about you both and want to see you happy now that you have the chance."