When Remus finally admits his feelings for Nymphadora, Sirius kicks the kitchen chair back and balances it on two legs with his hands behind his head, expelling all the air in his lungs with mock-disgust. "Love," he exclaims, pulling a face that reminds him of breakfasts with James and Lily in the great hall his seventh year at Hogwarts. Remus inclines his head to one side in a wolfishly inquisitive manner, and he's only too happy to clarify: "Bleck!" Remus is kind enough to smile and Sirius is again flooded with gratitude for this long-lost brother, for this understanding. There's no need to say things have changed. Across the noble-and-most-ancient kitchen table, the werewolf looks worn and tired, but genuinely content in new and unexpected ways. The sigh that Remus releases after the smile isn't one of long-suffering, or weariness, it's alive, magical, smitten. His old friend is quietly confident in ways that Sirius has forgotten that he could be.
"It's been a long time," Remus says, and then his eyes light with a mischief that Sirius associates with long nights in the forbidden forest, elaborate plans involving poltergeists and dungbombs, laughing so hard they can barely walk down the stairs, "it feels good."
And Sirius can only nod. He doesn't know. This is new territory and old territory all at once. Relinquishing Remus to Tonks will be harder in some ways than it was with James and Lily, easier in others. He knows how much time Remus has invested in keeping him company in this new prison —when he could just as easily be off somewhere enjoying the last tense days before the breaking of the storm with Nymphadora. Sirius needs him. Azkaban nearly killed one part of his soul— and coming back to the world meant losing James all over again, reconciling a lost thirteen years of his life, and swallowing all the guilt and frustration once the running was over. It's just as much due to Remus as it is to Harry that he's able to function, that he's regained humanity, and that the vengeance can be put aside (for a while) at all. So, it's bittersweet—this territory. Because the smile on Remus's face is enough for Sirius to want to push him out the door this instant after Tonks, to admonish him to never come back to this crumbling old hellhole unless it's for Order business, to move on with his life in ways that Sirius knows he'll never allow himself to do. Letting go is hard, he's found. Change is painful, but it's a new world, and a new life.
He sits across from Remus Lupin marveling inwardly at the journey he's on. And suddenly thinking of love as something more—it's all the things they had that can never be lost, no matter what rat tried to take it from them: late night pub-crawls, music and breakfasts, Quiddich injuries, the thrill of flight and dancing, wands to the wireless, witty answers to OWL essay questions, being at the height of power and feeling so fine that nothing could stop them, ready to eat up the earth and destroy anything that would threaten them, and later hope and resiliency and knowing that they were going to win because this kind of friendship could prevail over any evil.
James would know just what to say, and Peter would've expressed every emotion without any consideration, but Sirius can only let the chair fall heavily back into place on the stones, and give a barking laugh.
"Alright, Moon-the-Loon," he says, when he's sure he can say it without being overcome with an urge to weep, "but I'll have you know, I'm the best man."
Remus reacts with a customary blink of surprise, followed by a cool, unruffled honesty, "You always were, Pads."