Up until now, following a century-old decree by George V, only the eldest son of the Prince of Wales's eldest son could have the title prince. That would have meant that any daughter born to William and Kate would have been called "lady."
The declaration was signaled in the London Gazette Wednesday, although the Queen made the decision on New Year's Eve. And the decree covers all future children of the couple.
It says, "The Queen has been pleased by Letters Patentunder the Great Seal of the Realm dated 31 December 2012 to declare that all the children of the eldest son of the Prince of Wales should have and enjoy the style, title and attribute of royal highness with the titular dignity of Prince or Princess prefixed to their Christian names or with such other titles of honour."
The move is in line with the proposed changes in legislation to remove gender discrimination in the line of succession. The U.K. government and those across the Commonwealth have started the process of updating the laws so that a first-born girl could succeed to the throne regardless of whether or not she is followed by a boy.
Current rules would mean the boy would succeed to the throne.