A new documentary to celebrate Queen Elizabeth II’s 90th birthday is set to air and the royal family gave viewers a glimpse into the monarch’s life in time for her April 21 birthday. The Duchess of Cambridge even revealed Prince George’s name for his great-grandmother.

People reported that Britain’s ITV will air Our Queen at Ninety and in it, Princes Kate Middleton said in the documentary that when she gave birth to Princess Charlotte last May, the Queen was “thrilled” to have a great-granddaughter.

She said, “It’s very special having a new little girl” and said she felt “very, very lucky” to have a sister for Prince George. Revealing that Prince George called her “Gan-Gan,” the Duchess also said the Queen said when she returned to Kensington with Prince William after the birth, the Queen “was one of our first visitors here.”

In addition to talking about the bond the Queen has with her great-grandchildren, the Duchess also revealed that during visits, Queen Elizabeth will leave “a little gift or something in their room when we go and stay.”

Other members of the royal family who took part in the interview included Prince Charles and both of his sons, Princes William and Harry. E! News reported the two princes call her “granny.”

William said his grandmother allowed him to forge his own path and said having her “stability above me has been incredible.”

Prince Harry praised his grandmother for what she helped to accomplish among the 53 Commonwealth nations while Prince Charles lamented on the achievements she had made during her long years as monarch. He commented that he said to his mother, “Do you realize that when you reach 90, I shall have known you for 68 years?” He said this earned a chuckle from her.

According to The Associated Press, the Queen will have an official party to celebrate her birthday in June.

Our Queen at Ninety is set to air March 27 in the U.K. on ITV.