The only FF's that have convincing connections are FFVII-FFX and FFT-FFXII.

To a lesser extent there could be a case with FFT-FFVII. Not with (SPOILER)Cloud per se, since he arrives from outside Ivalice. Instead it is the (SPOILER)flower girl in Ivalice named Aeris (with the same character design no less). I take it to mean that Ivalice exists parallel to the FFVII Planet in different places, although not necessarily at different times.