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Beaufort Polo Club - Charity Day

TETBURY, ENGLAND - JUNE 16: Prince William, Duke of Cambridge takes part in a charity polo day at Beaufort Polo Club on June 16, 2013 in Tetbury, England. (Photo by Mark Cuthbert/UK Press via Getty Images)

Britain's Prince William

Britain's Prince William, the oldest son of Princess Diana and Prince Charles, turned 31 on June 21. The prince, also known as the Duke of Cambridge, is expecting his first child with wife, Catherine Middleton.