The family line was descended from FUJIWARA no Uona in the Northern House of the Fujiwara clan, and Onuki clan was a descendant of the Commander-in-Chief of the Defense of the North FUJIWARA no Hidesato, who subjugated TAIRA no Masakado.
家系は藤原北家の藤原魚名の流れを汲み、平将門を征伐した鎮守府将軍藤原秀郷の末裔にあたる。