Royal family Christmas photo
The Duke and the Duchess of Cambridge pose with their children, Prince George and Princess Charlotte, in a family photo released ahead of ChristmasKensington Palace/Twitter

Kate Middleton has revealed her feelings of being a mother of a daughter in a new documentary honouring Queen Elizabeth's 90th birthday. In the video, the Duchess of Cambridge also tells what Prince George calls his great grandmother.

"It's very special having a new little girl," Kate, 34, says in the video titled The Queen at Ninety by ITV. "I feel very, very lucky that George has got a little sister," she adds.

She also says the Queen, who will be 90 years old on 21 April, was thrilled to know that she had delivered a baby girl when Princess Charlotte was born. "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," reveals Kate, describing the birth of her daughter, who will turn one on 2 May.

The duchess further reveals that George calls the Queen "Gan-Gan". "George is only two and a half and he calls her 'Gan-Gan'," the mother-of-two says.

Kate also speaks of the Queen's love for the children and the royal family and how caring she has been. "She [the Queen] always leaves a little gift or something in their [George and Charlotte's] room when we go and stay, and that just shows her love for her family."

Kate's relationship with Queen

Recalling her first engagement with the Queen without Prince William in Leicester in 2012, the duchess says the latter was very caring and supporting. "She was very supportive. The fact she took the time to make sure that I was happy and looked after for that particular occasion, which probably in everything that she's doing is a very small element, it shows just how caring she is really."

Kate adds: "She's been very generous in not being forceful at all and in any of her views, but I feel she's been there, a gentle guidance really for me."