“Penny for your thoughts, Chapel.”

“Ever notice that Vash and Knives are never in the same place at the same time?”

“You’re not implying—”

“They certainly seem to insist on setting themselves apart, despite supposedly being twins: the way they act, the way they dress, the people they surround themselves with—”

“No way. That’s too crazy, even for Knives.”

“There’s only one way to find out.”

“You mean you’re going to—”

“I’ve already volunteered.”

“Damn. You planned this.”

“I have to know, Midvalley. If I’m wrong, at least there’d be a chance.”

“And if you’re right?”

“Then we’re all fucked.”

Unnecessarily Long and Tiresome Authoress’ Notes:
Yeah, yeah, both the manga and the end of the anime invalidate this theory, but it’s still a slightly scary thought.