Last names for Sora, Riku, Kairi, and other kids?

[Skyblade]

Your desire for references is going to ruin your chance at having good names. Since none of the characters have last names given to them in the game, you would do best not to introduce your own. Anyone looking at your work is likely going to be a KH fan to begin with, spotting last names at all will seem silly to them. For the names to be ones such as the ones that you suggested will ruin a lot of interest in your story. If you feel the need to have last names, I suggest picking out some fairly common and normal last names. Having your references will seem like a cheap ploy (Keyheart? Anyone will spot where you got that in half a second), and will kill the enjoyment of the story.

Also, a good many FF characters have no last names at all. Except for the characters of FFVII and VIII, I don't think any of them have last names. And in those games, the vast majority of the last names were totally meaningless.

I said that I don't want references to other characters.

I didn't say references to other characters. I said references. Whether they are references to the other characters or to the game's plot matters not, both will have a negative affect on whatever work you are trying to create. Now why don't you go back and read my post and try to understand that I am simply trying to help you improve your work, nothing more.