Even if we take the view that the relocation from Shimousa to Mutsu was factual, individual names mentioned in the family trees are not reliable, and the existence of Tanenaga remains doubtful.
下総から陸奥へという流れを大略認める説をとっても、系図の個々の人名は信用できるものではなく、胤長の実在性には疑問がある。