Tenei-in, the legal wife of the sixth shogun Ienobu, later designated Yoshimune as heir, and he was adopted by the shogun family for the first time from the Tokugawa gosanke, assuming the position of the eighth shogun of the Edo bakufu.
その後、6代将軍家宣の正室・天英院の指名により御三家出身では初の養子として宗家を相続し、江戸幕府の第8代将軍に就任した。