well you obviously know where cloud, tifa, aerith, yuffie, cid and sephirth came from - ff7.
setzer - ff6
squall, selphie, sefier, fuu (fujin), rai (raijin - ff8
vivi - ff9
tidus, wakka, yuna, rikku - ff10, paine (ffx-2)
the moogles have been in all ff games but the majority shown in kh are from ff9.
i dont think ive missed anyone?