The Great Fathers are the rulers of Bayasabhad, Kayakayanaya, and Shamyriana, the sole remaining cities of the now defunct Patrimony of Hyrkoon.
The Great Fathers are chosen from among the male population of these cities. While girls learn to ride and climb before they learn to walk and are trained in the arts of bow, spear, knife, and sling from the earliest age, ninety nine of every hundred boys, the sons of the Great Fathers, are gelded when they reach the age of manhood and live out their lives as eunuchs, serving their cities as scribes, priests, scholars, servants, cooks, farmers, and craftsmen. Only the most promising males, the largest, strongest, and most comely, are permitted to mature, breed, and become Great Fathers in their turn. Maester Naylin in his Rubies and Iron speculates on the circumstances that led to such customs.