The Yoshikawa clan was one of the Irie family that descended from FUJIWARA no Otomaro, who was the grandchild of FUJIWARA no Kamatari and the fourth son of FUJIWARA no Muchimaro of the Southern House of the Fujiwara clan.
吉川氏は藤原鎌足の孫で、藤原南家藤原武智麿の4男・藤原乙麻呂の流れを汲む、入江氏の一族である。