Japan’s parliament has passed a bill to relax imperial succession rules, amid concerns about the shrinking size of the imperial family.

The bill, passed by the upper house on Friday, allows the imperial family to adopt distant male relatives over the age of 15 and allows women to maintain their royal status after marrying outside the family.

But it does not change the law prohibiting women from ascending the throne despite widespread public support for an empress, meaning Princess Aiko, the current emperor’s only daughter, is still ineligible to succeed the throne.

The bill passed the lower house last week and will go through final legal procedures before the changes take effect.

Japan has the world’s oldest continuous hereditary monarchy, with a lineage believed to span more than 2,600 years.

Currently, first in line to the throne is Fumihito, 60, the emperor’s younger brother.

Fumihito’s son, Prince Hisahito, 19, is second in line.

The third in line and last eligible candidate for the throne is the emperor’s 90-year-old uncle.

Without any amendment to the law, the line of succession will end if Prince Hisahito does not have a male child.

However, with the new bill, male descendants of 11 former imperial branches could be adopted back into the family. These family branches had been eliminated after World War II.

Female members of the imperial family will also be able to retain their royal status if they marry commoners. They were previously forced to give up their titles and leave their families, which is what Princess Mako did in 2021 to marry her college sweetheart.

This will allow for a larger royal family that will be able to keep up with official duties such as attending court ceremonies and making public appearances. However, descendants of female members with commoners will still not be able to inherit the throne.