It is also assumed that they are either unmarried (for their entire lifetime) or formerly-married to an Emperor or a Crown Prince (widow, not remarried) (refer to Family Tree below).
また、未婚（生涯独身）か天皇・皇太子の元配偶者（未亡人、再婚せず）かのいずれかであったとされている（下掲系図を参照）。