there's really no more connection between XIV and XIV than there is XIV and any other FF game universe. each are their own dimension with their own laws of physics and the universe, and it is possible to cross between then (through the Interdimensional Rift) but is relatively uncommon.

recurring themes, motifs, people or places exist because, well it is the Final Fantasy franchise, but i think from a lore perspective, you can think of it as coincidences due to similarities in all the universes. like pretty much all of them have humans, after all.