Queen Elizabeth announced that if Prince William and pregnant wife Kate have a daughter, she will officially hold the title of princess.
The move updates rules introduced almost a century ago. Under a 1917 proclamation from George V, only the eldest son of William and Kate would have been called a prince.
A girl would only have had the title "Lady" and would not have been known as "her royal highness."
According to Reuters, the Queen put out a royal announcement to change this so that all of William's children would be treated the same.