[quote="Captain Cupcake"]I like to personally think that TLK is just its own entity, and that its film ended with the generic and genderless cub nicknamed "Fluffy." Everything else is just supplementary material that doesn't necessarily happen after(or in the third film's case, during) the original movie's events.[/quote]
I feel the same. At least it's a bit easier to ignore any faults in new material by thinking like that.
But yeah canonically it's Kiara and Kion, though that doesn't mean I don't enjoy AUs with Kopa or Chaka included, in fact I like them much better.