 His courtesy title was "Saikyō-no-daifu", and his Court rank was Junior Fourth Rank, Lower Grade.Nagakuni, known in his childhood as Hōzō () was born in Nihonmatsu on May 22, 1834, the 6th son of Niwa Nagatomi.On November 15, 1858 he succeeded to the family headship upon his father's retirement.