Knives does seem it, and it probably doesn't help that he seems to almost stalk around the edges of the connection, like a predator looking in on a collection of small, delicate animals. At least he's careful to let the boys take as much as they want, though his physical gaze seems to mostly be on Vash.

For a moment, Vash might sense a lot of the emotions that Knives keeps hidden. There's an almost unfathomable level of longing there, deep and dark.