Regulus found himself staring at Sirius again, trying to process everything Sirius had said. He felt a bit like he had fallen down the rabbit hole; of all the turns he had expected their conversation to take, this was not one of them.
"I was glad to help," he added, and then he strove for a lighter tone. "It goes without saying I'm also glad you hadn't gone mad."
He drew in a deep breath and released it slowly. "But things like that are what family are meant to do for each other, or so I would like to think. It seems to me we have both missed out on that for too long."
He hesitated, and then he placed his hand atop Sirius' where it rested on his arm. "I have been wary of being judged, of seeming weak or playing for sympathy, and not just with you. It's been with more or less everyone. I suppose old Slytherin habits die hard, and I forget not everyone is scrutinizing and dissecting my motivations at all times, but I really do want this brothers thing, as you put it, to work. It matters to me," he concluded simply.
It was the closest he could come to confessing exactly how much this meant to him without risking embarrassing himself or scaring off Sirius; emotional candor was not his forte to begin with, but he was trying.