However a son born to a concubine three years earlier was selected to the heir of shogun, Atsunosuke was adopted by one of gosankyo (three privileged branches of Tokugawa family), Shimizu-Tokugawa family.
但し、その3年前に側室が産んだ徳川家慶が将軍家世子と定められていたため、敦之助は御三卿の一つ・清水徳川家の養子となった。