But where does one draw the line? When Scott and Jean were first introduced, they were not dating. Then they were. That was a change. Should they have remained celibate forever, because they weren't introduced as a couple?
Ditto Rogue and Remy, or Kitty and Piotr. None of them introduced as couples. Should they remain eternal virgins, because 'don't change mah characters?'
There's always going to be a first time. And when that first time happens, whether it's with the opposite sex, the same sex, a couple of people or an alien egg-laying bird-lady space-princess, *it's going to be out of character,* because that particular character didn't have an established history of dating alien egg-laying bird-lady space-princesses.
Oh no, Xavier doesn't have a history of dating alien bird-ladies! It's totally out of character! They sprang it out of nowhere on us and shoved it in our faces! Couldn't they have made a new character who was dating an alien-bird-lady, instead of shoehorning this onto Charles?
Really, where is the line to be drawn. At what point in a character's life can they no longer grow or change or evolve or try new things?