Its direct founder was a descendant of a younger brother of Sadatsuna UTSUNOMIYA, Yasumune UTSUNOMIYA who accompanied Sadatsuna (supreme commander of the bakufu forces when Mongol invaded Japan), the eighth head of the Utsunomiya clan (the sixth head if Tomotsuna UTSUNOMIYA was the first head) to the Kyushu region and was based in Oki, Yamato District, Chikugo Province.
宇都宮氏第8代(宇都宮朝綱を初代とすれば第6代)当主宇都宮貞綱（元寇の時に討伐軍総大将）とともに九州に同行し、筑後国山門郡大木を拠点とした貞綱の弟である宇都宮泰宗の子孫が直接の始祖である。