At the RAF Akrotiti in Cyprus, Kate spoke to mother Rhian Davis who was carrying her 10-week-old baby at the time.
"She asked whether I was sleeping through the night and she told me that Louis is starting to wave," Rhian revealed to Hello!
At just three years of age, Kate’s daughter Charlotte has already mastered the royal wave and often steals the show with her performance.
At the event, Kate mentioned that she tried to show Charlotte and her eldest son George, 5, the festive treats laid out at Kensington Palace but by the time the kids arrived back from school everything was gone.
“We took the children down to where the party was, but everything was gone,” she said. “They were so disappointed!” Kate revealed to PEOPLE.
But George was excited that his parents were attending the event.
“I told George this morning we were going to see the pilots today, and he said, ‘If you see a helicopter, can you take a picture?'” William added.