The young royals call their granddad 'Grampa Wales' after his former Prince of Wales title, while the Queen Consort has previously revealed that they call her "GaGa."
WATCH: Prince Charles can't contain his laughter during official event
In 2016, she told the Daily Mail about her sweet nickname: "I don’t know if it's because they think I am [gaga]!" she said. "It is funny but is still very sweet."
During the Queen's Platinum Jubilee pageant in June, we also saw just how much of a caring grandfather Charles is as he kept Prince Louis entertained on his lap during one of his first big public appearances.
King Charles and Queen Consort Camilla share a close bond with the Wales children
The new King's wife, Camilla has grandchildren of her own, and she's also a step-grandmother to King Charles' grandkids.
Speaking about the important role during a Cornwall visit, the royal said: "Well, what's so lovely about being a grandmother, they teach you things and hopefully they learn a few things from us."
The kids also have a very sweet name for their father William, as they call him 'Pops' instead of dad, according by a report by People magazine. How cute!
Make sure you never miss a ROYAL story! Sign up to our newsletter to get all of our celebrity and royal news delivered directly to your inbox.