According to the family tree edited by Yoshikazu (義和) SAKUMA in Sendai Domain in the Edo period, Tanemochi is a son of Tanenaga and a grandson of Tanemichi, and his mother is a daughter of Taneyori TO.
江戸時代に仙台藩の佐久間義和が編纂した系図では、胤茂は国分胤長の子、胤通からは孫にあたり、母は東胤頼の女。