In 2015, pursuant to the 2011 Perth Agreement, the Commonwealth realms changed the rules of succession to the 16 thrones of Elizabeth II to absolute primogeniture, except for male heirs born before the Perth Agreement. The effects are not likely to be felt for many years; the first two heirs at the time of the agreement (Charles, Prince of Wales, and his son Prince William, Duke of Cambridge) were already eldest born children, and in 2013 William's first-born son Prince George of Cambridge became the next apparent successor.