It has almost the exact same mythos as the XIII series. Pretty much EVERY NUMBERED TITLE UNTIL NOW, has had different worlds and universes with no mythos or backstory on the universe in common with the other numbered titles. But now, that rule has been broken with XV and XIII. Maybe things will be different from now on. Maybe its like what Metal Snake said, that there is a timeline for all the FF games, and we haven't really been able to tell until now, when we start seeing similar mythos showing up in multiple Numbered titles.

Oh well. Can't wait for it.

It doesn't really matter though.

There's still the whole "Final Fantasy VII is a sequel to Final Fantasy X & X-2" thing  

Besides there has always been gods and other assorted things in the FF universe that are named the same like chocobos and numerous enemies and summons. It doesn't really matter. Plus we dont know what theyve changed about the mythos if anything. 

FF XV: Problem?

I did not see it coming. I'm glad that they're starting to finish the project up thought- More Kingdom Hearts for us!

AWESOMENESS it has exceeded my expectaions in every way possible. imo this blows LR:FFXIII waay outta the water as far as Action RPGs go