The royal pair were seen watching from the sidelines as William and his brother Harry competed in the annual Jerudong Trophy polo match. However, it looks like football is more like Prince George's thing.
While this is the first time we've seen George on his feet, the Duchess last week revealed that he'd already started walking independently.
Although it is still unclear exactly when the prince took his first steps, Kate couldn't keep the news to herself and had to share her son's achievement with fellow guests at a brunch with the America Cup yachting team in London.
The no doubt proud mother looked at ease in a breton stripe top teamed with blue skinny jeans and comfy flats as she played with her son on Sunday.
Meanwhile, the 32-year-old has also been busy redecorating her young family's country home - Anmer Hall, on Sandringham Estate - and is said to be very close to finishing the project.
Rumour has it this foray into interior design has led to Kate becoming completely obsessed with creating the perfect cosy getaway and, er, finding the perfect fireplace. But of course!
MORE! Check out more pictures of the royal fam in the gallery below.