UK Prime Minister David Cameron announced Friday that reforms of the Act of Succession, which dates back to the 17th century, have been approved, allowing a girl to inherit the throne before her brother.

“We will end the male primogeniture rule so that in the future the order of succession should be determined simply by the order of birth,” Cameron said at a meeting of Commonwealth leaders in Perth, Australia.

There are currently 16 nations which consider Queen Elizabeth II as their monarch and head of state. Each sovereign nation must adapt their laws independently.

"Attitudes have changed fundamentally over the centuries and some of the outdated rules - like some of the rules of succession - just don't make sense to us anymore.”

He also announced that the nations have agreed to scrap the rule that says “no one who marries a Roman Catholic can’t become monarch.”

"The idea that a younger son should become monarch instead of an elder daughter simply because he is a man, or that a future monarch can marry someone of any faith except a Catholic - this way of thinking is at odds with the modern countries that we have become," he said.

Nevertheless, the monarch himself or herself must be a member of the Church of England, of which he or she is the head.

They plan to work together with the 16 Commonwealth realms through an international group within each country to bring forward the necessary measures to implement the new changes at the same time.

With the approval of this act, for now on, the first-born royal child will inherit the thrown, whether boy or girl.