I want to understand this process, I have the PS3 version of the game, if I upgrade to the PS4 version I'll be unable to use the PS3 right? Then if I want my brother to play on the PS3 and me on the PS4 what should I do? The PSN account is linked to the game? Or if I uninstall it and re-install it he will be asked to link his SE account to his PSN account?

Probably is too confusing to undesrtand, I'll short:
-I have both version PS3 and PS4
-I want to use both, so my brother use PS3 and me PS4
-If i start the PS4 whit my PSN/SE account the PS3 version will no longer be playlable?
-If my borther try to log in on PS3 he will be asked to link his SE account to his PSN account or FFXIV is account lock?

I know is confusing, feel free to ask, I just want to understand what I need to do.

#If this is not the tread, please relocate.