He belonged to the lineage of the Akechi clan, and it is also said that Yorinori AKECHI, a brother of Sadaaki's father Yoritomo AKECHI, was also Mitsutsugu AKECHI, the grandfather of Mitsuhide AKECHI.
明智氏の系統であり、定明の父・明智頼明の兄・明智頼典を、明智光秀の祖父・明智光継と同一人物とする説もある。