(A/N: i don't own Harry Potter. spoilers for Deathly Hallows. this fanfiction is written by an atheist, but assuming that the wizarding world of Harry Potter has some form of afterlife because how else would the stone of the deathly hallows work? set in 1979)
They were having an Order meeting, although they didn't have a headquarters set up yet, so they were all currently sitting around a circular table in the Room of Requirement. Remus and James were next to Sirius, since Peter was unable to make it to this meeting, Lily next to James, and Arabella Figg and Dumbledore next to Lily. Hagrid was on Dumbledore's left and Sturgis Podmore, Mundungus Fletcher, Frank and Alice Longbottom, the Prewett twins, Marlene McKinnon, Mad-Eye Moody, Emmeline Vance, Elphias Doge, Edgar Bones, Dorcas Meadows, Dedalus Diggle, Caradock Dearborn, and Benjy Fenwick were all to the left of Hagrid.
There was recently a battle with the Death Eaters in Hogsmeade, and many of the highest ranking Death Eaters were there, including Bellatrix and Rabastan Lestrange, though thankfully there were no casualties on the Order's side. They were in a meeting a week after the battle when everyone was fully healed to make their individual reports to Dumbledore and the Order in case anyone learned anything useful.
Benjy Fenwick was making his report, and everyone but Mundungus were paying close attention. Benjy had a one-on-one encounter with Bellatrix Lestrange, and according to him she told him something that he thought the Order should know.
"While we were dueling, she said 'Don't try getting any of us to join your side, because they'll all end up like little Reggie. He tried to back out, and our Lord killed him after torturing him so much his mind broke.'" After he finished recounting what Bellatrix said, Sirius went very pale, though it seemed that no one noticed. "I think we might still be able to use this information to stop people from joining him in the first place, if we let people know that they won't be able to get out if they join." Benjy continued.
"I think we should be more concerned at the fact that we haven't heard of a Death Eater that could be known as 'Reggie'," said Remus. "If we don't even know who our enemy is, despite the fact that they clearly think we already know them, we're even less informed than we thought," he finished.
"It could mean that we have a traitor in our midst, someone not telling us everything," Mad-Eye said suspiciously, his electric-blue eye sweeping over all of them, landing on Sirius, Moody being the first person to notice something off about him.
"Now, now, Alastor, if there was a traitor amongst us Bellatrix wouldn't think we already know who this 'Reggie' is," said Dumbledore, trying to quell the panic that just the suggestion of a traitor brought. "Is there something you'd like to share with us, Sirius?" Dumbledore followed with, finally seeing Moody's magical eye locked on Sirius and noticing how distressed he looked.
Everyone immediately turned their gaze to Sirius, most of them still not trusting a member of the Black family.
"Regulus... he's... a relative. My little brother."
James and Remus' eyes widened in recognition, remembering the very few times they heard Sirius mention him, but also recalling that Sirius always seemed protective of him, and how guilty he felt when he found out Walburga and Orion made him join the Death Eaters after Sirius left.
Nobody other than the Prewett twins, Lily, and Dumbledore felt the slightest sympathy for Sirius, thinking that since Regulus was a Death Eater he deserved what he got, whether he tried to back out or not.
"Professor Dumbledore, I'm sorry, but could I be... excused, for a moment?" said Sirius in a shaky voice, but understandably the most put-together one he could mange at the moment.
"Of course, dear boy. In fact, I think it best if you go home for tonight, you can tell us anything you learned at the next meetng. James or Remus, if one of you would like to go with him? You may report at the next meeting as well."
James offered to take Sirius home, and, after giving Lily a kiss on the cheek, pulled Sirius up by his right shoulder, and when he swayed slightly on his feet, put an arm around his shoulder and Apparated, not to Sirius' flat, but to his house in Godric's Hollow that he lived in with Lily.
James immediately guided Sirius to the nearest chair, knowing he probably wouldn't be able to keep himself together for much longer now that he wasn't being watched by the Order. He grabbed Sirius a glass of water, then went back to the room he was seated.
"Hey, Pads, listen, I know you're hurting, but it wasn't your fault," he said, knowing from the red and watering eyes what his friend was thinking after spending all of their time together for eight years.
"Prongs, if I hadn't left Walburga and Orion wouldn't have made him take my place as a Death Eater." "There you have it then, it's their fault, Siri, not yours. You have so many people who are more at fault for this than you are. Voldemort, Walburga, Orion, hell, you could even blame Snape, considering he's the reason you had to go back there that Christmas," James responded, trying so hard to stop his best friend from blaming himself. "Pads, before I make you get some sleep, I want you to know that Regulus loved you just as much as you love him, and he wouldn't blame you for this. Now, lets get you settled in the guest room."
James tugged Sirius to his feet, put his arm back around him, and guided him to the guest room.
Later, after Sirius had a nightmare and cried his heart out on James' shoulder, Lily came home to find them both asleep on the couch in the living room and covered them both up with a blanket. James, Remus, and Lily slowly helped Sirius to truly stop blaming himself for his brother's death, but their work was soon forgotten when James and Lily died and Sirius and Remus both blamed Sirius for their death, and then Sirius' bad memories forced him to start blaming himself for his brother's death again. When he got out, he still blamed himself for it, and never really stopped, since after Remus learned Sirius was innocent, he never realized that Azkaban didn't just stop wounds from healing, it tore the old ones back open, too. Sirius died with all of his wounds from before Azkaban torn open, despite having them healed once before. They never fully closed in death, either.