The first Shogun, Ieyasu, in order to maintain the bloodline in the event that the Shogun household died out, for supervision and control of the Daimyo nationwide, and for support of the Shogunate, established three branch households of the Tokugawa family that were allowed to use the Tokugawa name, and sent the ninth son, Yoshinao TOKUGAWA, to the Owari domain, the 10th son Yorinobu TOKUGAWA to the Kishu domain, and the 11th son Yorifusa TOKUGAWA to the Mito domain.
初代将軍家康は将軍家が断絶した場合の血脈の維持や、全国の大名統制への監視、および幕府への補佐への意味も込めて、将軍家同様に徳川姓を名乗ることが許された徳川御三家を設置し、9男の徳川義直を尾張藩、10男の徳川頼宣を紀州藩、11男の徳川頼房を水戸藩に封じた。