The family tree edited by Sakuma shows that the mainstream of the Kokubun clan originated in Mutsu Province started with Tanemichi and succeeded by Tanemochi, however, these names are not referred to neither in the family tree prepared in Shimousa Province nor in the family tree owned by the Furuuchi clan in Mutsu Province.
国分氏の本流は陸奥国にあって、胤通から胤茂に伝えられるというのが佐久間編の系図のいうことなのだが、下総側の系図にも、陸奥側で古内氏が蔵した系図にも、こうした人名は出てこない。