The Black brothers always knew to keep each other included. Even when things started to change big time, they still acted like it was like when they got sorted into diffrent houses.
But now the war was on, people were dying. Yes, they were only reading about it for now. But also preparing to get out to the real world. So their "including each other" move wouldn't work no more once they were actually out at the opposite sides, and they knew it. So when Regulus got his mark even before 17, it hit Sirius that this was going to be the beginning of rest of their relationship. So here they were out of their dorms at night. They were arguing and neither of them were giving up this time. Aware of the distance between them. Cold blood affecting the younger Black all the way down now that he made his decision.
"It doesn't matter which side you are on! Neither of them care about "all" people's lifes, i am not gonna sit still and be a good boy, just for everyone else to think we ARE something, in their side. And i am not gonna stay on the side that stops you for selfish reasons from actually saving someone. Reggie!-"
"dont call me that." Regulus said, blankly.
"-don't you see who you are loyal to?! Is that it? Are you gonna be her pet, just listening and believing everything she says??" Sirius just continued, almost begging, begging to be safe with him.
The younger one dark shoved his arm of the robe up, making his dark mark visible. "They don't stop anyone from anything. At least i could actually make sure my loved ones are safe while i am actually out doing something-" he said. Stopping when Sirius suddenly turned to him.
Sirius looked frozen maybe a bit dissapointed, like he couldn't believe his little brothers priorities.
"You mean killing other people instead of protecting your loved ones, protect is first, not attact- thats the whole purpose-"
"WHAT İS? What is the purpose of not killing those savages! You said it too, we should kill when its necessary and now it is, what is stopping you from it Sirius!?" Regulus yelled, finally on the edge, he looked desperate. A sixteen year old boy that wants the people dead, his hopes are long gone.
"Well sorry i can't focuse on killing because i am too busy protecting. I want my loved ones alive more then i want 'them' dead."
"-like That ever did you any good!" Regulus snapped.
And stopped when he realised what he just said. Silent followed and even the empty corridors felt still then ever. Cold then ever.
Sirius froze in tracks, flashbacks to when he failed, he fell weak and failed. When he put his friends in danger on purpose. Hurt his most loved one, because he wanted to show that git his lesson. Not being able to prevent harm from happening, to the one he prmised to protect and be next to.
"i- im sorry i didnt-" Regulus broke the silence with hurried cold words. Still keeping his walls up.
Hex!
Faster than a heartbreak.
Regulus hissed in pain, his words cut short. He looked at his brother, only to find an expression he never wanted it to be towards himself ever.
"You-" Sirius hissed, anger showing in his voice talking to his brother, while guilt is visibly agonising him deep inside too.
"Sirius! No- Just- don't you see what it takes, its only gonna give them place to-" he tried.
"THEM?! Them??" he grinned, unlike how he always did, with bitter humor in it. "You - Are - "Them"." he stated, unmercifully. Taking a few steps forward to his little brother, getting reallly close to his face. Look of indignation.
"You made yourself them, so if you think i should stop protecting my loved ones since i'm SHIT at it. And focuse on killing more, like the monster i am, -i was supposed to be-. Then i suggest you make sure i don't see your face ever again. Because i won't hesitate to kill you from the other side." he said, the ends close to whispering threateningly.
He backed away, releasing his grip on the boy's collar, which he didn't realised when he hold it.
Sirius did take one final look.
A cold cautious stare. Hoping that the sixteen year old would never feel familiar to him ever again, nor like a brother.