Kunishige's earliest ancestor was Sanemoto DATE, a brother of Harumune DATE, who was the grandfather of Masamune DATE (grand-uncle of Masamune), so his family lineage was distantly-related to the lord of the domain.
始祖は伊達政宗の祖父伊達晴宗（はるむね）の弟（政宗からみれば大叔父）にあたる伊達実元（さねもと）という藩主遠縁の家柄。