The OKUBO Family was hereditarily succeeding the position of Shinto priest of Omikunitama Prefectural Shrine (Iwata City, Shizuoka Prefecture), one of Shikinai-sha (shrine listed in Engishiki laws) since the times of ancestors, so his father, Tadanao OKUBO, was also Guji (chief of those who serves shrine, controls festivals and general affairs).
大久保家は代々式内社である県社淡海国玉神社（静岡県磐田市）祠官家で、父の大久保忠尚もやはり宮司であった。