According to "Inaba no Kuni Ifukube no Omi Koshi," the genealogy of Ifukube clan compiled by Ifukube no Tomishige in 784, Ifukube no tsumuji is the child between his father, Ifukube no kujira and his mother, Kumahime, and he is the twenty sixth generation of the Ifukube clan.
延暦3年（784年）に伊福部富成が編纂した同氏の系譜である『因幡国伊福部臣古志』によれば、父伊福部久遅良（くぢら）と母熊媛（くまひめ）との間の子で、同氏の26代目当主にあたる。