Britain's government is pushing its plan to change the rules on royal succession to provide equal treatment for princes and princesses.
The government says it is trying to convince every Commonwealth nation where Queen Elizabeth II is head of state to modernize succession.
Under the proposed plan, the first child of Prince William and the Duchess of Cambridge would eventually become monarch — regardless of gender.
Prime Minister David Cameron said Wednesday he had written to the 15 other states ahead of talks at a Commonwealth summit in Australia later this month.
The changes would scrap a rule that puts boys ahead of their sisters in the line to the British throne, and lift a ban on British monarchs marrying Roman Catholics.
Cameron's office said the queen would not part of the discussions.