LONDON (AP) - If Will and Kate's first child is a girl, it's now clear that she'll probably become queen one day - and not even getting a little brother can mess that up.
The Commonwealth countries agreed Friday to change centuries-old rules of succession that put sons on the throne ahead of any older sisters. So that hypothetical daughter of Prince William and Kate Middleton - now known as Catherine, Duchess of Cambridge - would have a prime place in history: the first princess to beat out any younger brothers and accede to the throne.
Had these rules been in place in the 1500s, Henry VIII would have just been a rather large historical footnote.
The move is a baby step: Before taking effect, the changes still must be approved by the legislatures of the 16 nations where Queen Elizabeth II is head of state. Still, the agreement, which was reached at a meeting of Commonwealth nations in Perth, Australia, represents a triumph over practices now considered outdated and sexist in much of the world.
Nations including Sweden, Belgium, the Netherlands and Norway have already taken similar steps.
Will and Kate's lavish April wedding renewed a decades-long debate over succession. Middleton told a well-wisher in Canada this summer that she hopes to start a family. William has said the same.
Historians think it's about time to change the rule.
"You shouldn't muck around too much with the constitution, but it's a good idea to change this at this time," said royal expert Hugo Vickers. "It's much better to have it sorted out before any babies come along."
The new rules would only apply to future heirs and would have no impact on the current line of succession.
William is second in line to the throne after his father, Prince Charles, who is the queen's firstborn child. Charles' sister, Anne, is lower in the line of succession than her younger brothers Andrew and Edward by virtue of their male gender.
Charles had only sons, William and Prince Harry, so the issue of gender was never raised.