Prince Louis Is 4! Every Sweet Detail We Know About the Little Royal: 'He's Always So Happy'

He's only 4 years old, but we already know quite a bit about birthday boy Prince Louis. Here is everything we know about the little royal so far.

1. He was born on April 23.

It's a very patriotic birthday, as it's also St. George's Day — England's national day.

2. His name is Prince Louis Arthur Charles.

All three of his names are a nod to family members.

3. He weighed 8 pounds, 7 ounces at birth.

That's more than either Prince George or Princess Charlotte weighed when they were born.

Prince Louis

4. He was born at the Lindo Wing at St. Mary's Hospital.

The hospital, located in London's Paddington neighborhood, is where both his siblings were born as well as his dad.

5. He went home the same day he was born.

And mom Kate Middleton was nothing short of unbelievable when she stepped out holding little Louis just seven hours after giving birth.

6. He's fifth in line to the throne.

That's after grandpa Prince Charles, dad Prince William, big brother Prince George and big sister Princess Charlotte.

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7. His name has family connections.

Not only is it one of his dad's middle names, it's also a nod to Louis Mountbatten, Prince Louis's great-grandpa Prince Philip's uncle, who was a father figure for Charles and was assassinated in 1979.

Arthur is one of William and Charles's middle names, while Charles, of course, is his grandpa's name.

Other royal visitors? Queen Elizabeth, Grandpa Charles and uncle Prince Harry and aunt Meghan Markle.

8. William and Kate waited four days to announce his name.

That's likely so they could introduce Charles to his new grandson in person.

9. He's a good sleeper.

That's according to dad William, who said that Louis was "behaving himself" at an Anzac Day service. However, William was also caught nodding off during that same service!

10. He's got some famous fans.

Like Louis Tomlinson, who tweeted that he'll take his fellow Louis "under my wing." He also got a hello from former First Lady Michelle Obama, who tweeted that she can't wait for their "Kensington Palace pajama party."

11. He missed out on Meghan Markle and Prince Harry's royal wedding.

While his older siblings George and Charlotte served in Harry and Meghan's bridal party, little Louis stayed home during the festivities, while mom Kate made her first official post-baby debut.

12. He almost slept through his royal christening.

He was totally undisturbed when his mom carried him into the Chapel Royal at St. James's Palace on July 9 and napped in her arms even as greeted Archbishop of Canterbury Justin Welby, who led the ceremony. "Let's hope he stays like this!" Princess Kate told him.

13. Big sister Princess Charlotte adores him.

In one of his christening portraits, Charlotte devotes all her attention to Prince Louis, holding his hand and staring at him in awe — definitely a sweet moment for the family's biggest show-stealer!

14. His smile is irresistible.

Little Louis's gummy grin was the best part of the last official christening portrait shared with the public. In fact, it was so sweet that Will and Kate decided to release it, even though it was taken only for the family to see.

15. Louis is George's mini-me.

The littlest member of the family is the spitting image of his big brother in portraits released by the royal family in November to honor the 70th birthday of Prince Charles. Louis' pinch-worthy cheeks, a trait George and Charlotte were known for as babies, are display as he's held by Kate.

16. His hair is darker than his siblings' locks.

Louis seems to be taking after his mom! Although George is a blonde like his father and grandmother, Princess Diana, the little prince's locks appear to be growing in darker.

17. Louis already has a bond with his grandfather.

Louis grabs hold of Prince Charles' hand in a sweet photo, which appeared in the BBC One documentary, Prince, Son and Heir: Charles at 70. It's no surprise, as William says in the documentary that his father is "brilliant" with the children.

18. He mastered his family Christmas card debut.

The Cambridges released their first holiday photo as a family of five – with Prince Louis looking directly at the camera while cuddled in his mom's arms. The holiday portrait was taken in early fall at their country home, Anmer Hall in Norfolk.

19. The little royal has crawling down pat…

Kate shared an exciting update on her 9-month-old son while talking with the crowd gathered outside the Victoria and Albert Museum in Dundee, Scotland, in January. Photographer Mark Stewart, who was among those capturing the visit, says that Kate told a woman that "Louis is a fast crawler."

20. …and is always on the move!

"Louis just wants to pull himself up all the time," Kate told fellow parents during her March visit to the Henry Fawcett Children's Centre. "He has got these little walkers and is bombing around in them."

21. His two front teeth have come in

The little prince showed off his toothy smile in his first birthday portraits (taken by mom Kate!). Louis looked like the perfect combination of his two older siblings in the adorable shots.

22. Louis is a happy baby!

"He really is the most cheerful, smiley little boy – he's always so happy and content," a source tells PEOPLE of Prince Louis.

23. His royal wave is already impeccable

Prince Louis made his Trooping the Colour debut on the Buckingham Palace balcony in June 2019. He wasted no time in showing off his royal wave…and rarely ever took a break from greeting the crowd!

24. One of his first words was a sweet nod to beloved British cook Mary Berry.

"One of Louis' first words was 'Mary,' because right at his height are all my cooking books in the kitchen bookshelf," the royal mom said.

25. His favorite song is a classic

Kate shared that "Happy Birthday" is "one of Louis' favorite songs."

26. He causes some trouble for his parents during video calls

While adjusting to new life under lockdown during the coronavirus pandemic, like millions of other families, Kate and Prince William have been turning to video calls to keep up with family members. However, it seems that Prince Louis can't resist inadvertently cutting off the chats!

"For some reason, he sees the red button and he always wants to press the red button," William told the BBC.

27. He's already made his first royal speaking appearance...

In Oct. 2020, Prince Louis joined his older siblings in asking TV icon and naturalist Sir David Attenborough a question about the natural world. Louis sweetly asked, "What animal do you like?"

28. ...and made his red carpet debut!

Kate, Prince William and their three kids walked the red carpet in Dec. 2020, when they attended a pantomime performance at the London Palladium. Little Louis looked around him in awe at all the activity while holding his mom's hand, then took a seat on Kate's lap to watch the show.

29. He's on the move.

To celebrate his third birthday in 2021, Kate and Prince William shared a photo of Prince Louis posing on a red walker bike.

30. Sometimes it's hard to keep up with him!

In addition to his bike, Kate shared that Prince Louis is "very quick," especially on his scooter.

During a call with a young girl named Mila who participated in Kate's Hold Still: A Portrait of Our Nation in 2020, the royal mom said, "Louis has gotten so big now — he's very quick running around. And he's on his little scooter as well. He's very quick. I can't keep up with him!" "

31. He's started school.

The little royal's first day of preschool coincided with the week of his third birthday. He's attending Willcocks Nursery School, the same place as his big sister Princess Charlotte.

32. His passport already has some stamps.

For their 2021 Christmas card photo, Kate and Prince William chose a family portrait taken during a private vacation in Jordan, meaning Prince Louis is already a world traveler!