There are two stories about his origin (roots): one is that he was a child of Myobo hakase (teacher of the law in the Ritsuryo system), NAKAHARA no Hirosue and a brother of OE no Hiromoto, and the other is that he was the third son of FUJIWARA no Mitsuyoshi and became an adopted son of NAKAHARA no Hirosue.
出自については、明法博士・中原広季の子で大江広元と兄弟であるとする説と、藤原光能の三男で中原広季の養子になったとする説がある。