User blog comment:Silver-Haired Seireitou/Bleach Reveals: Light Novels and Databook Translations/@comment-18812574-20180428114607/@comment-18812574-20180428130253

Also as a minor clarification: According to the Spanish Bleach wiki (which does in fact treat the light novels as canon material): "Who is the Soul King? What was the world like before his arrival? These are questions without answers that the people of the Soul Society will sometimes ask. They would say that, if life after death exists, it isn't as perfect as they say when we are young: the image of living in Heaven at God's side after death is only a dream, and the Soul Society is truly more like a purgatory [more than] eternal life. The nobles, ever since their youth, are taught that they are superior to the rest of the souls and that the Soul King is the catalyst of the three worlds. If he was not there, the Human Realm, Hueco Mundo and Soul Society would collapse and open the gates of Hell. Because of this, the world began when the Soul King appeared...

The Tsunayashiro clan prided themselves on being the most powerful clan, and during the years in which the Soul King was worshipped, they showed their complete loyalty to him. It then goes on to say that a child with a highly inquisitive nature was born who always asked questions related to the origin of the world, was constantly reading/exploring old ruins, and because of his interests that set him apart from the Gotei 13, he eventually left his division. Then: This child is now the adult that had become the leader of his clan: Tokinada Tsunayashiro—the one who had discovered the origin of the world. But to reach his goals he still lacked power, and he would only achieve what he wanted by dominating the three words.

So that's to say that, the Tsunayashiro seem to be the most powerful clan that sort of led the four other clans, but I didn't see any info on them being the record keepers. Tokinada's goal is also interesting. That said, there seems to be a lot of conflicting information regarding the details of CFYOW. I wish an official translation had been published.