It was likely a testament to just how off Sirius was feeling that he allowed Regulus to order him around, not just going back with him to his room, but sitting and not arguing so much of what he'd said. Because there was a lot that came out of his brother's mouth that left Sirius wanting to argue with him simply because it grated him so much, regardless of how he ever actually felt about any of it. But he sat and exhaled in a rush, leaning forward his elbows on his knees and his head in his hands when Regulus tried to talk him up, or at least his version of it.
"I think I could be both." He said feeling a little bit out of control for all that Regulus was doing what he could to try and help him pull it together. He could be both Sirius Black and unstable all at the same time.
He exhaled shaking his head, "You're not going to get me to say I regret that I let them into my life, you know." He warned his brother. "I don't know if this place is the right place for me." Or if any place was for that matter. Not when he was feeling like this.