Five's not asking just to annoy Klaus, he only has a simple idea of what his brother's powers are and most of that bows down to 'those powers sucked'. So he wants to understand them a bit better and see if that could help Klaus in some way.

"I know. But you can tell me, I believe you." Five's voice sounds a bit like a croak, so he doesn't raise it to make himself easier to understand. "Do they just scream? Or they want something from you? Perhaps there's a way to convince them to leave you alone."