Prince George of Cambridge
Prince George is almost two and a half as he starts nurseryGetty Images

Kate Middleton, 34, has revealed what her eldest son Prince George, who is two and half years old, calls his great-grandmother Queen Elizabeth II. The revelation was made by the Duchess of Cambridge in her first TV interview since she got engaged to Prince William in 2010. The couple married in 2011.

"George, who's only two and a half, calls her Gan-Gan," Kate said while speaking on ITV special Our Queen at Ninety that will air in the UK on 27 March. The queen will celebrate her 90th birthday on April 21. Prince Harry, 31, and William calls the queen "Granny" Kate said.

In 2015, Kate and William, 33, welcomed their second child, Princess Charlotte. "It's very special having a new little girl...I feel very, very lucky that George has got a little sister. The Queen was really thrilled that it was a little girl, and I think as soon as we came back here to Kensington Palace she was one of our first visitors here," Kate said, according to The Telegraph. "She always leaves a little gift or something in their room when we go and stay. That just shows, I think, her love for her family," she said.

Kate in the interview also praised the queen for helping her with her royal engagements. "She's been very generous and not sort of being forceful at all in any of her views," she said. "I feel she's been sort of a gentle guidance, really, for me," she added.

"I said to my mother the other day, I said, 'Do you realize that when you reach 90, I shall have known you for 68 years?'" the queen's son and William's father, Prince Charles, 67, says in the special. "She had to laugh a little bit."