Consequently, Katamori was in a very good position to be adopted out to a senior member of the Tokugawa house. This opportunity presented itself in the form of Matsudaira Katataka, the 8th generation lord of the Aizu domain. Yoshitatsu readily approved of the adoption, not only because Katataka was the lord of a more senior house with a distinguished history and lineage, but the fact that Katataka was his birth brother must have also entered into the equation.[3] Consequently, the young Keinosuke was adopted by Katataka, and married Katataka's daughter Toshihime, in 1856.[3] Following his adoption, Keinosuke assumed the name "Katamori", which made use of one of the characters from his adoptive father's name.