Although it is stated in Imperial Family Law, 'a male member who belongs to Imperial family;' an issue appeared that there are no male Imperial successors in the direct line of the present Imperial family, there is only a female successor, after Imperial Princess Aiko was born.
皇室典範の「皇統に屬（属）する男系の男子」という条文について、愛子内親王の生誕など天皇直系の皇位継承者の終端に女性しかいない問題が生じていた。