His father was FUJIWARA no Tadayoshi (藤原忠能) who was Sangi (councilor) known as In no Kinshin (the retired Emperor's courtier) of the Emperor Shirakawa and the Emperor Toba, and Naganori was his second son.
父は白河天皇・鳥羽天皇の院近臣として知られる参議藤原忠能で、長成は次男にあたる。