[q=Square Enix website]In April 2003, two of the video game industry’s leading companies, Square Co., Ltd. and Enix Corporation, merged to form a new company, Square Enix Co., Ltd. (Square Enix).[/q]
[q=GameFAQs website]Final Fantasy X - Square Enix - 07/19/01 JP[/q]
[q=GameFAQs website]Final Fantasy X-2 - Square Enix - 03/13/03 JP[/q]
[q=GameFAQs website]Kingdom Hearts - Square Enix - 03/28/02 JP[/q]
As you can see (assuming that GameFAQs is correct with its information), Enix didn't have anything to do with those games, unless they helped before the official merge.

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By the way, it says "Square Enix" because of the merging, not because Enix may have had someting to do with it.