The Keepers were once members of the Church of the Force, its body consisting of non-Force sensitive beings that followed the way of the Jedi. After the Sacking of Tuanul, a pastor of the church feared that its members would be hunted down by the First Order and eliminated, as the Jedi had been following the Clone Wars. As a result, he urged his community to flee to the harsh world of Burska, where he believed they would be safe to continue walking the path of the Jedi. The congregation agreed to follow the man and the community has continued to keep and preserve the traditions of the Jedi Order, living in caves on the tundra planet for the last century.
Away from the Church of the Force, the believers started calling themselves Keepers and sought to not only revere the light side of the Force, but to protect it too. They were determined not to be victims, as their brothers and sisters on Jakku had been.
So, decade after decade passed, the severe cold of their new home hardened them. They trained to become fighters, acquiring weapons and armor, all while still keeping to the Jedi Code. New life was brought into the world while others passed away, the settlement existed...endured. It was all they aimed to do. Past goals of restoring the Jedi Order were gone. To them, their saving grace was that they were not attuned to the Force as the Jedi were, sparing them from the complications that inevitably led to the downfall of the sacred Knights.
Creating a non-FS religious faction that was once a part of the Church of the Force that will allow members to be more involved with the war that is being waged in the galaxy.