According to Senjoryo (the regulations for the recruitment and promotion of government officials), ranks were bestowed upon the descendants when they become over the age of 21, and those eligible for oni were children and grandchildren of Koshin (Emperor's family), the children of the emperor's great grandchildren, descendants of shoshin (retainers) who were higher than third rank, and children of those who were higher than the fifth rank.
選叙令によれば、子孫が21歳以上になったとき叙位され、蔭位資格者は皇親・五世王の子、諸臣三位以上の子と孫、五位以上の子である。