Archie Mountbatten-Windsor's birthday marked by Duke and Duchess of Cambridge

The Duke and Duchess of Cambridge are among the members of the Royal Family who have wished Prince Harry and Meghan Markle's son, Archie Mountbatten-Windsor, a happy third birthday.

Kate and William posted a photo from Archie's christening on their social media channels, with the caption: 'Wishing Archie a happy 3rd Birthday today.'

The Queen's official Royal Family Twitter account also wished little Archie "a very happy 3rd Birthday!", accompanied with a cake emoji and another picture from his christening.

The image features Meghan holding him in her arms, with her mother Doria Ragland, Prince Harry, Prince Philip and the Queen all looking on adoringly with smiles on their faces.

The Clarence House Twitter account, for his grandfather Charles, shared the same image, with the caption, "Happy Birthday Archie!", complete with a balloon.

Archie's royal relatives haven't seen him since his parents quit as senior working royals and started a new life in California, making these re-shared moments on his big day all the more special.

The Queen is also still yet to meet Meghan and Harry's youngest, 11-month-old Lilibet, the family nickname of her great-grandmother.

Read more: Will Lilibet be christened in Britain? It's a no, says royal source

In the Duke's speech at the Invictus Games opening ceremony, he spoke of the fatherly advice he gives his son.

"When I talk to my son, Archie, about what he wants to be when he grows up, some days it’s an astronaut. Other days it’s a pilot. A helicopter pilot obviously. Or Quasi….from Octonauts…..," he said.

"But what I remind him is that no matter what you want to be when you grow up, it’s your character that matters most.

"And nothing would make his mum and me prouder than to see him have the character of what we see before us: YOU."

Read more: It's wonderful to be back' says Meghan, on first public appearance with Harry since Lilibet's birth

Meghan has also previously spoken of her son's "voracious appetite for books", revealing that he was a big fan of her own book The Bench.

"Archie loves the book, Christian I haven't told you... he loves the book, which is great because he has a voracious appetite for books," she said in a conversation on NPR's radio show Morning Edition Sunday with journalist Samantha Balaban and her illustrator Christian Robinson.

Read more: The Duke and Duchess of Cambridge's bridesmaids: Then and now

"Constantly when we read him a book he goes, 'Again, again, again and now we can say, 'Mummy wrote the book for you, it feels amazing."

Last month, the Mirror reported that Prince Harry and Meghan told the Queen she will get to see her great-grandchildren "in the near future" in a brief visit to London to see her.

Watch: 5 things you never knew about Archie Mountbatten-Windsor