She is also patron of the All England Lawn Tennis and Croquet Club, which hosts the world's most prestigious annual tennis champion.
If you needed any further proof that five-year-old Prince George is truly living his best life, look no further than the news that the mini royal has been receiving private tennis coaching from none other than legendary player, Roger Federer.
This week has also been a momentous week for Kate and her daughter Princess Charlotte, as her four-year-old royal will attend her last day at nursery and will soon be seen attending her big brother Prince George's school in September.
It may sound insane that the royals, of all people, would recycle clothing, but Kate reportedly loves to pass clothes down from one child to the next, as demonstrated in many of her photos of the kids.
She said: "It's brilliant to have the opportunity to sit there and chat to her and talk about Fed cup and British players and I guess just everything and anything about tennis".
The Duke and Duchess of Cambridge's children are officially on their summer vacation. "She'll be like his older sister", Williams added with a smile.
The duchess is expected to take her seat in the royal box later on Tuesday, which usually features famous faces and celebrity fans of the sport.
I was really sporty when I was little, less so now that I've got lots of babies.
The mom of three looked elegant and laid back at the same time in a white dress with black buttons, which was custom designed by London boutique Suzannah.
Kate is a longtime tennis fan and appears at Wimbledon annually.
Now Roger Federer is playing his part in helping to further the prospects of a Next-Gen player from Britain's royal family - one who is likely to end up being known as King George VII.
Williams and her husband Alexis Ohanian are friends of the Duke and Duchess of Sussex and attended their wedding in 2018.
He told the show: "Anne was just saying, "What a special day" - and (Kate) is such a good ambassador for tennis".