His need to sit down wins out quickly enough over his pride, so he takes the invitation for what is and sits down on the bed, trying to ignore the building headache.

Good question. Why does he want to know? It's not something he particularly wants to pry into, though it has stoked his curiosity, but something beyond simple curiosity is urging him on to ask. At this point, he'll do a lot of things to not think about how sick he feels, about--about dying.

"I've not seen you so glad before," he ventures. Then again, he doesn't see Killua that much at all, when he's not coming by Hel to see Bran. "I wanted to know more of him, but if you'd rather not speak of it, I won't try to sate my curiosity."