However, his father, Yoshishige, was killed in the battle of Zemmyo tsutsumi in 1561, and his brother, Sadashige ITAKURA, who had succeeded their father as head of the family, was also subsequently killed in 1581 in the fighting at the battle of Takatenjin-jo Castle in Totomi Province, where the army of the Takeda clan had hidden themselves, which resulted in Katsushige becoming the next head of the family, under orders from Ieyasu TOKUGAWA.
ところが1561年（永禄4年）に父の好重が善明提の戦いで戦死、さらに家督を継いだ弟の板倉定重も1581年（天正9年）に武田氏軍の籠る遠江国・高天神城攻め（高天神城の戦い）で戦死したために徳川家康の命で家督を相続した。