Hypothesis: fairy tales originally come from accounts of vampires.

Assuming that fairy-tale nobility are Twivamps explains so much. They can "live happily ever after" because they're genuinely deathless; they're supernaturally beautiful; the beautiful peasant-girl that the noble prince falls in love with is turned, the magically healing kiss is actually a bite (or maybe just a kiss -- vampires have venom instead of saliva, right?); they fall in love at first sight and stay that way forever.

Prince Charming is a vampire.