Prince Louis of Cambridge's most adorable moments

Prince Louis of Cambridge came into the world on St. George's Day, his mom Duchess Kate's reported due date, and the little brother to Prince George and Princess Charlotte was cute as a button – despite being the Prince William and Kate's largest baby to date at 8 lbs 7 oz!

The little one's full name, Louis Arthur Charles, is steeped in significance. Louis pays tribute to his great-grandfather Prince Philip's great-uncle, Earl Mountbatten, who was killed in 1979 by the IRA. The name, which is of French and German origin and means "renowned warrior," is one of William and Prince George’s middle names.

Click through to see all of the sweetest photos of Prince William and Kate's third child...

Photo: © Getty Images

In December 2019, little Louis was spotted in the back of his parents' car as he arrived with his mom and dad and big brother Prince George and Princess Charlotte to the Queen's annual Christmas lunch.

The then-one-year-old looked adorable in a very seasonal sweater – and looked just like both his big brother and his mom!

Photo: © Max Mumby/Indigo/Getty Images

Royal watchers were thrilled when Kate brought Louis, George and Charlotte to watch their dad play polo against uncle Harry in July 2019! We couldn't help but coo at seeing the one-year-old sucking his thumb while the Duchess of Cambridge carried him across the Billingbear Polo Club grounds.

Photo: © Max Mumby/Indigo/Getty Images

Just before that photo was taken, Louis, who was just learning to walk, had been seen toddling over to investigate the horses with his mom!

Photo: © Samir Hussein/WireImage

He even got to say hi to one and give the magnificent beast a pat! So sweet!

Photo: © Max Mumby/Indigo/Getty Images

Louis was also spotted enjoying lunch with his big brother and sister.

Photo: © Samir Hussein/WireImage

Louis also stole his mom's sunglasses and entertained Kate and aunt Meghan as she held his baby cousin, Archie!

Photo: copy; Max Mumby/Indigo/Getty Images

About a month earlier at Trooping the Colour, Louis made his balcony debut and thrilled royal watchers with his adorable wave!

Photo: © Max Mumby/Indigo/Getty Images

Little Louis also couldn't stop sucking his thumb then, and Kate was really trying to get him to quit!

Photo: © Max Mumby/Indigo/Getty Images

Louis and his siblings were spotted looking out Buckingham Palace's windows just before the parade started. George looked pretty amazed by how many people were outside!

Photo: © Max Mumby/Indigo/Getty Images

On April 22, the day before his first birthday, Prince William and Kate released three adorable portraits of Prince Louis.

Photo: © Instagram/@kensingtonroyal

They captioned the adorable snaps: “The Duke and Duchess of Cambridge are delighted to share these new photographs of Prince Louis ahead of his first birthday tomorrow.”

Photo: © Instagram/@kensingtonroyal

The little prince showed off his bright personality, crawling through the forest near the Cambridge's Norfolk home.

Photo: © Instagram/@kensingtonroyal

On Dec. 14, the Cambridge family released a perfectly casual photo for their Christmas card! Prince Louis totally stole the show in this one, showing off his adorable little grin for the camera.

Photo: © Matt Porteous

To commemorate Prince Charles' milestone 70th birthday, the Duchess of Cornwall, the Cambridges and the Sussexes all gathered at Clarence House to pose for casual portraits together. And we just can't get over how cute baby Prince Louis looks, having a grab at grandpa Charles's nose!

Photo: © Chris Jackson / Clarence House via Getty Images

Prince Louis is clearly taking after his siblings' electric personalities! The newborn smiled gleefully in the arms of his mom, Kate, in a special fifth christening portrait released by the palace.

Photo: © PA/Matt Porteous/The Duke and Duchess of Cambridge via Getty Images

The Cambridges posed for their first-ever portraits as a family of five on the day Prince Louis was christened. Prince George and Princess Charlotte grin happily, while Kate gazes down at her baby boy and Prince William shows off his megawatt smile.

Photo: © Matt Holyoak/Camera Press

The newborn royal's christening portraits were absolutely stunning. His mom, Duchess Kate, looked down lovingly on her third child as he looked around the gardens and held onto his mom's chest.

Photo: © Matt Holyoak/Camera Press

In one of the first glimpses of baby Prince Louis on his christening day, Duchess Kate held her new baby boy while walking into St. James's Palace in London.

Photo: © DOMINIC LIPINSKI/AFP/Getty Images

Prince Louis looked serene as he slept in his mother's arms as the Cambridges arrived for his baptism. Fans delighted in seeing how much the little one had grown since his first official portraits were released at the beginning of May 2018.

Photo: © DOMINIC LIPINSKI/AFP/Getty Images

Even though conversation was going on around him between mom Kate and the Archbishop of Canterbury, Justin Welby, who performed his christening, Prince Louis dozed in his mother's arms.

Photo: © DOMINIC LIPINSKI/AFP/Getty Images

Kate revealed little details about 11-week-old Louis' personality at his christening, saying that he's "very relaxed and peaceful" before adding with a smile: "I hope he stays like this!" Photo: © DOMINIC LIPINSKI/AFP/Getty Images

In the first photo of the royal siblings, Princess Charlotte planted a kiss on newborn Prince Louis' forehead. The two photos shared on May 6, just a few weeks after William and Kate welcomed their third child, celebrated his birth and Charlotte's third birthday.

Photo: © Getty Images

Louis looked absolutely adorable in his first portraits as a newborn baby.

Photo: © Getty Images

Hi little angel! Prince Louis's white hat was from Spain, where his nanny Maria Teresa Turrion Borrallo is from.

Photo: © Getty Images

The newborn stayed warm in a white heirloom blanket and matching bonnet.

Photo: © Getty Images

Kate snuggled her little one tight when he made his debut to the world on the Lindo Wing steps, before the doting mom took him back inside to make sure he stayed warm enough.

Photo: © Getty Images

Little Louis went home from the hospital in the same Britax Römer car seat that his big brother Prince George and big sister Princess Charlotte used. The cozy white cover was from Spanish brand Pasito a Pasito.

Photo: © Getty Images

Those cheeks! The little one definitely shares some of his siblings' features.

Photo: © Getty Images

Just a few hours old and already melting hearts around the world... including his mom Kate's!

Photo: © Getty Images

Baby Louis was sound asleep despite embarking on his first car ride!

Photo: © Getty Images

The little one slept soundly in his car seat as he was carried to Prince William and Kate's new seven-seater Land Rover to be taken home to Kensington Palace.

Photo: © Getty Images