He became the adopted heir of Chikayoshi HIRAIWA, one of the Sixteen Heavenly Generals of Tokugawa and Fuyaku (a warrior who educate the son of the Lord to become a great leader) through the good offices of Ieyasu who was concerned about Chikayoshi having no heir.
徳川信康の傅役で徳川十六神将の一人だった平岩親吉に嗣子がいないことを憂えた家康の配慮で、親吉の養嗣子になった。