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The royals, they're just like us … sort of.

In April, the famous family sat down with BBC for a documentary called "Our Queen" to commemorate the 90th birthday of Queen Elizabeth II. In the film, the family gets candid, but also reveals how normal they are.

Of all the things that were discussed, one thing is standing out: Prince George calls the Queen "Gan-Gan."

The level of informality — and genuine cuteness — is surprising, even for a two-year-old.

Duchess Kate revealed that news and the Internet is going crazy over the admission. But, perhaps this isn't all that surprising.

According to royal biographer Kitty Kelley (via Popsugar,) "Gan-Gan" is the name that generations of royals have used to describe their great-grandmothers. In fact, Prince Charles apparently used the term to refer to his great-grandmother Queen Mary, the mother of Queen Elizabeth's father King George VI.

Kitty said Prince William and Prince Harry actually called the queen's mother, Queen Elizabeth the Queen Mother, "Gan-Gan" until her death in 2002. Harry even let his nickname for his great-grandmother slip during his own cameo in the documentary.

Film crews also spoke with other royals, including Prince Charles and and Prince William, about the the longest-reigning British monarch.

Kate actually opened up quite a bit in speaking about the Queen and raising her royal family. She said the Queen was "thrilled" when she and William welcomed Princess Charlotte last May.

"It's very special having a new little girl … I feel very, very lucky that George has got a little sister," she said. "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."

"George is only 2 ½ and he calls her 'Gan-Gan,'" Kate said. "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."

So, while it's not totally original for George to call the monarch "Gan-Gan," it certainly doesn't make it any less adorable.