Of course, Regulus thinks, of course Sirius notices. He doesn't visibly tense at the question but there's a slight hunch to his shoulders that is probably very familiar and is definitely very instinctive.

It's not as though he can lie about it being there though, so he has to turn toward his brother with a faint, fake smile drawn across his face.

"It would be," he says, evenly. "Yeah."