Remus could always tell when Sirius had had a fight with his family.
Those were the nights he laughed too loud, smiled too large, partied too hard. His eyes would flick back and forth maniacally, like a caged animal, desperate to escape the confines of his own mind.
Inevitably, he succeeded, and inevitably, Remus would get up from his quiet corner to help Sirius up the stairs. He would hold back his long hair as he puked and trace soft circles on his back while the other boy cried. After the drinking and the vomiting and the sobbing, Sirius would collapse into Remus' arms and the other boy would carry him to bed, dropping a soft kiss on his forehead before going to his own bed and falling into a light sleep, always keeping an ear open in case Sirius cried out during the night
Sometimes Sirius would tell him what had happened. More often, Remus would have to figure it out himself, either by asking Regulus or by patching together the parchment shreds he found on the ground. They never mentioned those horrible nights; no thank yous were exchanged. No, what ran between them was deeper than thank-you's, and no words would ever express it.
Because on the morning after the full moon, when Remus slowly surfaced to consciousness thinking he was dying because living could not be this painful, he would feel a hand, impossibly gentle, running through his hair, gently massaging his scalp. The other hand would be tightly clasping his own, anchoring him, reassuring him that he was human again and no longer wolf. In those minutes immediately after waking, Sirius was Remus' entire world. Sirius' touch, his concerned grey eyes, he gentle voice soothing and calm… all of these sheltered Remus in a womb of love and caring, pushing the angry world far from his awareness until he was ready to emerge.
They helped each other live, and eventually they lived for each other.
Remus would never forget that full moon after Sirius was disowned – waking up and seeing those grey eyes mere inches away. As they neared, Remus could see a single tear, beautiful in its solitary pride, clinging to his dark eyelashes. A moment later he felt that same tear on his cheek, but only as a whispered afterthought of eyelash grazing cheek. Remus' mind was far more interested in the soft pressure against his lips.
They had not needed to talk about that incident. It happened, as seasons happen to the earth, and as the seasons go on in an endless circle, so their relationship progressed naturally, effortlessly. When a number of seasons had passed, Sirius did not even have to as Remus to move in with him; he simply looked up from the onion he was chopping and greeted him with a dazzling smile as Remus trudged in, huffing and puffing under the weight of the trunk he was carrying.
It was only natural, then, that Remus and Sirius should die as they had lived: together. The war had taken many things from them – family, friends, fortune, careers – and it had even managed, at one point, to dim the flames of their love. Their only wish was that the war would not force them to live a minute without the other. And it didn't.
It should have been an ordinary raid on one of Voldemort's encampments. It would have been had not seven unexpected Death Eaters surged from the shadows. The minutes were hours as the spells flew, and when one hit REmus, Sirius begged Shacklebolt to take him away, help him, heal him… a severing spell to the leg had made Shacklebolt's mind up and he disapparated, leaving Sirius to face the three remaining Death Eaters.
Fierce fighter and skilled wizard though he was, Sirius could not hold them all off along. It was with a sense of detached resignation so very near to relief that Sirius saw the green curse speeding toward him. He raised his wand – too late…
As Sirius' lifeless body hit the ground in an isolated clearing in Ireland, a hundred miles away in a bed in Saint Mungo's, Remus' heart stopped beating.