As Razan HAYASHI mentioned that Ieyasu TOKUGAWA was an Imperial descendant (it means Ieyasu was one of Seiwa-Genji or Minamoto clan), generation difference is not considered.
林羅山が「徳川家康が（清和源氏であると言う意味で）皇胤に当たる」と唱えたように、世代の遠近は問わない。