Soon after his birth, Kunimatsu was looked after by the Wakasa Kyogoku family and, later, became an adopted son of Yazaemon, a whetstone shop owner in Wakasa, with whom Kunimatsu's wet nurse married again.
国松は生後すぐ若狭京極氏に預けられた後、乳母の再嫁先、若狭の砥石屋弥左衛門の養子となる。