"Lucky for both of us no one else has thought of that fact. Or just think it's suiting them instead." He's compartmentalizing, a little. But it's fine because the happiness is real. He squeezes Sirius back, glad enough to be moving to another room. Once they're there he'll immediately settle to sit, wincing and squeezing the outside of his own thigh to try and settle the muscles there.

"Not actually sure why it's happened. There was... A potion. Had to drink the whole thing and there was no way to bring a sample. It..." He frowns then, brow furrowing. "It was quite bad, and Dumbledore said that it's one of the lasting effects. We don't know yet if there will be others."

Don't know if he will be able to tell Regulus drank it or not. He doesn't say this, either. It's not important.