Well, in Kurt's case, it's pretty believable. He is, after all, blue, furry and has a tail. Which may make him a fetish lovers dream in some circles, but in general he's used to being a pariah, let alone an object of desire.
On the other hand, Claremont developed him into a swashbucklin man of action who's had his share of princesses and pretty ladies. I remember the first time they showed a very sultry Amanda Sefton talking suggestively to Kurt on the phone while in a bubble bath and being stunned (and then thinking "I better not let my parents see THIS." :)