Toshizo's older sister, Nobu SATO, was married to Hikogoro SATO, who was also their cousin and Nanushi (headman of the city) of Hino-jyuku, Hino city; it is said that Toshizo often visited the residence of Hikogoro.
歳三の姉佐藤のぶは姉弟の従兄弟でもある日野市日野宿名主の佐藤彦五郎に嫁いでおり、歳三も彦五郎宅にはよく出入りしていたと言われている。