Kate Middleton opens up about the Queen’s special bond with Princess Charlotte and Prince George in her first solo interview

In a new ITV documentary that marks Queen Elizabeth’s 90th birthday on April 21, titled The Queen at Ninety, the Duchess of Cambridge, née Kate Middleton, talked about the monarch’s special relationship with her great-grandchildren, Princess Charlotte, 10 months, and Prince George, who will turn 3 in July.

“George is only two-and-a-half and he calls her ‘Gan-Gan,’ ” the 34-year-old royal reveals. “She always leaves a little gift or something in their room when we go and stay and that just shows her love for her family.”

In her first solo interview since 2011 Catherine also opened up about the Queen’s delight when she found that her great-granddaughter Princess Charlotte came into the world on May 2.

“It’s very special having a new little girl. I feel very, very lucky that George has got a little sister,” Prince William’s wife says. “The Queen was really thrilled that it was a little girl, and I think as soon as we came back here to Kensington she was one of our first visitors here.”

Last year in May, Queen Elizabeth II also gushed about her great-granddaughter, several days after her birth, during a garden party at Buckingham Palace.

“We love to have another girl,” the monarch, who is a great-grandmother to Charlotte Elizabeth Diana, Mia Grace Tindall, Savannah Ann Kathleen Phillips, Isla Elizabeth Phillips, and one great grandson, George Alexander Louis, told guests.

The ITV documentary The Queen at Ninety will air in the U.K. on March 27.