The royal family are renowned for their generous use of nicknames.
From 'Gan Gan' to 'Cabbage' - and of course 'Lilibet', there's always some kind of unique moniker to take up in place of a formal name.
For Duchess Catherine - it seems she's all for getting on-board the family tradition.
At a recent royal event for the G7 Leaders Summit in the UK, the Duchess was seen greeting Prince Charles as "Grandpa".
Of course, this is no doubt the name used by Kate's three children for the future King - and the use of the name comes at high time given Charles has just become a Grandpa to another little one - Harry and Meghan's baby girl Lilibet.
According to the Daily Mail, Kate was heard greeting Prince Charles by saying: "Hello Grandpa! How are you?" as the Prince made his arrival.
The family attended a reception for the G7 leaders at The Eden Project in Cornwall on Friday evening - with Kate and Charles joined by the likes of The Queen, Prince William and the Duchess of Cornwall.
World leaders including Joe Biden, Justin Trudeau and Boris Johnson were also in attendance.
At the event, the Queen celebrated her formal birthday celebrations by cutting a cake with what we could only describe as a large sword.
She also wore a beautiful green and pink-toned dress with a floral print.
Kate meanwhile looked fashionable as ever in a white coat dress, wearing her long hair loosely.