Kate Middleton still calls Prince Louis 'my baby' although he's a 'proper boy now'

Adorable!

We love to know the sweet pet names shared between the royals.

Whether it's Prince George's sweet nickname for his dad, the Queen's secret codename, or Prince William and Kate Middleton's monikers for their children.

While Prince Louis may not have a moniker we know of, the Duchess of Cambridge still considers her youngest child as "my baby", even though he is four years old, and she has recognised he is a "proper boy".

Speaking during a visit to Little Village's hub in Brent, which is part of London's baby bank network, Duchess Catherine shared the sweet remark.

According to PEOPLE, Kate said: "I keep thinking Louis is my baby, but he's a proper boy now."

Prince Louis has started to join his siblings Prince George, nine, and Princess Charlotte, seven, and their parents on royal engagements.

The youngest of the Cambridge family was seen at the Queen's Platinum Jubilee celebrations, sitting with his grandfather Prince Charles. 

Louis, like his older brother, has proved to be quite the entertainer at royal engagements, as he is often pictured pulling funny faces at outings, which has seen him described as a "cheeky monkey" by friends of the family.

A source close to the royal family previously told PEOPLE: "He's a cheeky monkey — a typical third child. It's nice that the world got to see him enjoying himself."

Not only is Louis taking on his siblings quirky habits of pulling faces and entertaining the crowds, but he also has an interest in sports like his brother and sister.

According to The Mirror newspaper, the Duchess revealed that the four-year-old has followed in the footsteps of his older siblings, Prince George and Princess Charlotte, as well as his mum, by learning how to play tennis.

While chatting to Wimbledon champion Novak Djokovic, Kate was asked if Prince George plays tennis. According to The Mirror, the Duchess responded by saying: “George is playing. They’re all playing, even Louis who’s four. They’re all keen.”