While Kingdom Hearts is heavily inspired by Final Fantasy, with characters, themes, and mechanics borrowed from the series, Sora is an original character created specifically for Kingdom Hearts.
However, there are some notable exceptions:
* Final Fantasy VII: Advent Children: A small cameo of Sora's "Heartless" form (a creature from Kingdom Hearts) can be seen in this movie.
* Final Fantasy XV: A hidden code in the game allows players to unlock a special Sora costume for Noctis, the main character.
While these references are fun for fans, they don't mean Sora is actually a character in the Final Fantasy universe.