As Edwin mentioned, canon wise at the current place in the story, only the player's character is the Warrior of Light. And adding further to that, this was a question that the development team answered back during the Lore Panel at the very first FanFest and Ferne replied that a little suspension of disbelief is needed - that from the player's perspective, their character is the Warrior of Light, with every other player character just a regular adventurer.

Also, it should be remembered that apart from 1.0 characters who had the 'Legacy' story, the player's character is not actually called the Warrior of Light until the end of the initial 2.0 story - the first time is Minfilia mentions offhandedly that their constant exploits make them seem to be "a Warrior of Light reborn", but it is Hydaelyn Herself who first addresses us as such after Lahabrea is banished from Thancred. After all, the very term was first being used to describe the adventurers (ala 1.0 players) who fought at Carteneau but then vanished thanks to Louisoix's last resort, but because of the amnesia caused by said teleportation magic (and Bahamut's banishment), the memories possessed by those who remained behind of those adventurers' identities were obscured "as if by a bright light".

Either way, the important thing is that for story purposes, only the player's character is the 'Warrior of Light' from the player's perspective.