Since the end of Heian period, persons from the Hirata family of the Nakahara clan line were often appointed to this post, and in the late stages of the medieval times, this post became a hereditary post of the Hirata family, though some persons of other families such as the Abe family were appointed in the meantime.
平安時代末期以後は中原氏流の平田家が多く任命されるようになり、途中阿倍氏など他氏が任命されることもあったものの、中世後期に入ると平田家による世襲が確立した。