SHB's main scenario reveals that Ardbert is
the player's character, in that both share the same soul, and he ends up Rejoining his soul to the WoL's during the climatic scene prior to facing the final boss, curing them of the Light inside them that was about to transfrom them into a Lightwarden. This is why Minfilia refused him to sacrifice himself to stopping the Flood of Light a century before - she knew he still had a final task ahead of him to Rejoin with US, trusting in our natural tendency to overcome the impossible and that we would eventually make our way to the First to do so.
As for Ardbert's friends, they're Warriors of Light in a sense, in that they too possess the Echo and gained Crystals of Light, but they are not part of
us, they would have their own counterparts on the Source accordingly. They are not part of
our WoL, think of them as being parts of
other players from your point of view.