Member nations of the British Commonwealth have agreed to repeal a centuries-old rule that favors sons over daughters to take the royal throne, even if the daughter is the oldest born.

The agreement was reached Friday on the sidelines of the 54-nation Commonwealth Heads of Government Meeting in the western Australian city Perth. The meeting brings together all nations once linked to the former British empire.

The leaders of 16 nations which have Queen Elizabeth as their monarch also agreed to scrap the rule that bans the heir to the throne from marrying a Roman Catholic.

The changes were offered by British Prime Minister David Cameron, who called the rules outdated and senseless.

The rules have been under scrutiny since the marriage earlier this year of Prince William, second-in-line to the British throne, to Kate Middleton.

The three-day Commonwealth meeting opened Friday in Perth amid concerns about the group’s relevance in the 21st century. The 85-year-old Queen Elizabeth told the leaders in her opening remarks the meeting “promises to bring new vibrancy” to the grouping.

Australian Prime Minister Julia Gillard urged her counterparts to make this year’s meeting memorable for giving the Commonwealth “the direction it needed at a time of global uncertainty and risk.”

The leaders will discuss such issues as climate change, the high rate of child brides in many Commonwealth nations, and laws that criminalize homosexuality.