Japan will unlikely allow princesses or their offspring to ascend the Chrysanthemum Throne, preferring instead to induct unmarried men into the imperial family from cut-off collateral branches.
Imperial princesses are barred from ascending the throne by virtue of their gender, which means Emperor Naruhito's daughter Princess Aiko, 17, is out of the running. There are now only three heirs. First in line is the Emperor's younger brother, Crown Prince Akishino, 53. He is followed by his 13-year-old son Hisahito, and then the Emperor's uncle, Prince Hitachi, who is 83 years old.
Discussions on how to maintain the imperial family's longevity were halted after Hisahito was born in 2006, with the bloodline secured for at least another generation.
On Wednesday, a conservative group in Prime Minister Shinzo Abe's Liberal Democratic Party suggested allowing unmarried men of the defunct collateral branches back into the family. Eleven collateral branches of the imperial family were dissolved in 1947.
But the men are now in their third generation and grew up as commoners, said Dr Kenneth Ruoff, an expert on Japanese modern history at Portland State University.
"This is the way preferred by the far-right but it is fraught with problems. First and foremost, it is not in the least bit clear that any of these people want anything to do with the proposal," he said.
While polls consistently show the public to be amenable to the idea of a female monarch, it has been dismissed by a minority of right-wing conservatives with outsized influence in the government over fears that it will taint a bloodline that can be traced back to the mythical Shinto sun goddess Amaterasu.
But there are now only 18 imperial family members, with six princesses who will lose their royal status when they marry.
To address the shortage of working-age members who can perform official duties, female members may be allowed to lead imperial family branches, even as their offspring continue to be barred from the throne.