Not necessarily, he could be putting on a facade for her because of some... deep family reason and as a result he really is that way to everyone else except her. ;x PLUS out of the home town he no longer would have to... impress anyone so he could be himself?
Or MAYBE he does the jerky things that he does BECAUSE of her. For some weird reason (and assuming he is a jerk in the first place).
I dunno, I've seen it before, so it could happen