He's looking pretty confused himself, eyes searching the man's face for what meaning he's surely missing here. He starts when it's just lain out simply like that; you're dead too.

"...You're dead?" The watching, the floating...

"Wait! Hang on. I'm pretty sure what you just said is a little insulting but I'm going to let it slide because it's not technically untrue. You're a ghost?! Like a real actual ghost ghost?" Sorry muchacho, he's just got to take a second to wrap his head around this. And then once he does, he's frowning again. "But then... are you... haunting your sister?"