FUJIWARA no Otsugu's father played an important role in supporting two emperors, Emperor Konin and Emperor Kanmu, however, he died of disease while he was acting as a Sangi (royal advisor) when Otsugu was five years old.
父は光仁天皇・桓武天皇の2代の天皇の擁立に活躍したが、緒嗣が5歳の時に参議在任中に病死する。