Please fix your tags. Kingdom Hearts OST is name of the album not the artist. The music might appear in-game but is not made by the game.
Kingdom Hearts (キングダムハーツ, Kingudamu Hātsu?) is a hybrid action-RPG that was released in 2002, which is notable for being the result of a collaboration between the video game developer and publisher Square and Disney. The game combines characters and settings from Disney's animated features and films with those from Square's Final Fantasy RPG series. Although the game's primary plotlines follow characters who were created specifically for Kingdom Hearts, characters from both companies play major roles in the game and its storyline. The game features real-time rendered backgrounds and scenery.