Queen Elizabeth is about to celebrate her 90th birthday on April 21. In celebration of this major milestone, a new documentary titled Our Queen at Ninety is set to air in the U.K. In a teaser video for the upcoming program we get a preview of Kate Middleton's first television interview since her engagement to Prince William. The Duchess shares a few need-to-know details about the her two perfect royal children, Prince George and Princess Charlotte, and their great-grandmother—like Prince George's nickname for Her Majesty, and the special, adorably grandmotherly affection the Queen has for Princess Charlotte.