Matthew Kimble is not in love with his sister. Seriously, that's just gross.
Yeah, they're somewhat closer than siblings are supposed to be and they both definitely have issues but, come on. Matthew is not in love with his sister.
I mean, yeah, sometimes when he forgets himself, he leans in close (too close) but she doesn't even notice. She continues prattling on about whatever is bothering her this week, never missing a beat, and he'd be lying if he said he didn't care (of course he says it anyway).
Anyway, he can feel her hair against his cheek and maybe he doesn't pull away immediately, but the point is that he does and there you have it. Matthew is definitely not in love with his sister.
Maybe sometimes he still gets close (too close) and he hasn't forgotten a damn thing, but that doesn't mean anything. Honestly, it doesn't.
He's just lonely sometimes and Christine is and always has been a cuddler and it's totally okay for siblings to lean on each other if they need it. We would not be having this conversation if Matthew was a girl, would we?
We probably still would if Christine was a boy, but that's not the argument here. Matthew Kimble is sometimes (always) an effeminate man, and there's nothing wrong with that. (Well--) Nothing.
So what if Matthew enjoys his sister's company and her hugs and her laugh and the smell of her hair (his sister) and the way her hand feels on his arm (she's his sister) and that special way she smiles when-- (she's your sister)
She's his sister. Christine is his sister.
So it's agreed. Matthew Kimble is definitely not in love with his sister.
(The meaning behind the recurring dream in which they are happily married in Mexico, however, is a totally different conversation. Matthew never put much stock in dream-reading, anyway.)