Recent but undated handout photo issued on Friday July 22, 2016 by William and Kate, the Duke and Duchess of Cambridge, of Britain's Prince George at Sandringham in Norfolk, England, who celebrates his third birthday on July 22. (Matt Porteous/Handout via AP)

Recent but undated handout photo issued on Friday July 22, 2016 by William and Kate, the Duke and Duchess of Cambridge, of Britain's Prince George at Sandringham in Norfolk, England, who celebrates his third birthday on July 22. (Matt Porteous/Handout via AP)

Recent but undated handout photo issued on Friday July 22, 2016 by William and Kate, the Duke and Duchess of Cambridge, of Britain's Prince George at Sandringham in Norfolk, England, who celebrates his third birthday on July 22. (Matt Porteous/Handout via AP)

Recent but undated handout photo issued on Friday July 22, 2016 by William and Kate, the Duke and Duchess of Cambridge, of Britain's Prince George with the family dog Lupo, at Sandringham in Norfolk, England. Prince George celebrates his third birthday on July 22, 2016. (Matt Porteous/Handout via AP)

To mark the future king‘s third birthday today (Friday), his parents Princess Kate and Prince William released a new set of photos, as they did for his little sister Princess Charlotte‘s first birthday in May. (Matt Porteous/Handout via AP)