Why does he respond to every one of his (not really) sisters' attacks? I dunno, maybe because they've been clamjamming him all these years? Dude has zero experience with and less than zero resistance to a female, whether he's been raised with her or not. Only defense he has is to internally reject everyone, regardless of their appeal or his desire. What he needs is the chance to pursue something of his own accord and gain some kind of understanding of his own wants before anyone has any chance at all of breaking through,
And that's never gonna happen with these girls.