It makes his breath catch just slightly, to have Remus reaching out and grabbing at his sleeve right now. It hurts more than he could possibly imagine, knowing Remus has done exactly this for Regulus. Knowing that they're happy and Sirius giving any indication he's otherwise could break that.

He can't help that Remus' words make something crack in him. He tries his best to keep himself smiling.

"Well-- yeah," he manages feebly, "We're mates. We-- care about one another. We've got each other's backs. I-- I love you, 'nd-- you love me."

And he can manage to say it just like he does to James or Peter or Regulus. He can.