They are known as simply Master Archie and Miss Lilibet Mountbatten-Windor. But when Prince Charles one day becomes King, his grandchildren will become the rather grander Prince and Princess.The change will occur because under Royal rules the grandchildren of the monarch are automatically styled Prince and Princess.The rule was brought in back in 1917 by Harry’s great-great-grandfather, King George V.
He issued an order stating that only those in direct succession to the British throne, the children and grandchildren of the monarch, could be given the titled His (or Her) Royal Highness.
It stated: "The grandchildren of the sons of any such Sovereign in the direct male line (save only the eldest living son of the eldest son of the Prince of.
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