In 1765, due to his cousin and the feudal lord of the head family, Sadakatsu MATSUDAIRA, suddenly falling ill, he was adopted by the head family and next day succeeded the head family.
明和2年（1765年）、従兄弟で宗家藩主の松平定功の急病によって養嗣となり、翌日本家を継承する。