[El's POV: ]
From what we know there were around twelve members of the royal family that had started the barrier all those years ago and after they found out there was no need for the barrier around some three hundred years ago, they started living a normal life and through intermarriages among themselves, they were able to create their own little family of around a hundred people that lived in that relatively large space.
Then, one day, a strange illness started spreading among their people that couldn't be treated with their holy powers and thanks to that, people started dying.
'Lastly, only one family of four remained.'
A couple that was one of the few originators of their people, members of the original royal family, who had a relatively longer lifespan than the others of their family due to their stronger holy powers, and their children who were pretty young compared to the other children of their parents' relatives, had also inherited their powers.