As we all know Viera are a very matriarchal race, so during Ishgard's rise as a city state his family had originally migrated in from the mountains, his great (x4) grandmother already traveling with his great (x4) grandfather and several others of the family, found their place within the city as bookkeepers and damn good ones at that, which in turn brought great interest of their collection from the church. In the founding of the high houses, House Freyja was born, nomadic bookkeepers made into archivists, keeping every tome, scroll and the like safe for the city, housing a collection of some tomes even Sharlayan would be envious of. The family stayed with the matriarchal ways; the countess leading the family as it's head of house, continuing that line with every daughter born into the family, which was how the line stayed until Kuro was born. Although his sister was the older of the two and already lined up to be the heir. It was the first time in years it had been siblings made up of a brother and sister rather than two sisters.

I hope this answered your question well enough hehe <3