Prince Louis, the youngest son of Prince William and Kate Middleton, the Duke and Duchess of Cambridge, lovingly received several birthday wishes from his relatives on social media. However, the Royal Family Twitter account made an awkward blunder in the birthday message for the prince, who turned two years old on April 23.

The Royal Family Twitter account posted that Prince Louis is "The Queen's seventh great-grandchild." However, the youngest Cambridge prince is actually the sixth great-grandkid as there was another royal birth just two months after he was born.

Zara Tindall, the Queen's first granddaughter, gave birth to her second baby, Lena, in June 2018, making Lena the seventh great-grandchild. To date, Queen Elizabeth has eight great-grandkids in total: Savannah Anne Kathleen Phillips, Isla Elizabeth Phillips, Prince George, Mia Grace Tindall, Princess Charlotte, Prince Louis, Lena Grace Tindall and Archie Harrison Mountbatten-Windsor. 

Queen Elizabeth has eight grown up grandchildren as well. Peter Phillips and Zara Tindall (nee Phillips) are the children of Princess Anne, the Princess Royal. Prince William and Prince Harry are the Wales boys and the direct heirs to the throne as the sons of Prince Charles and the deceased Princess Diana, the Prince and Princess of Wales. 

Princess Beatrice and Princess Eugenie are the daughters of Prince Andrew and his ex-wife Sarah Ferguson, the Duke and Duchess of York. Lady Louis and James, Viscount Severn are the children of Prince Edward and Sophie, the Earl and Countess of Wessex. 

The royal grandkids and great-grandkids usually spend their summers at the Queen's summer home in Balmoral, Scotland. However, it's unclear if this plan will change this year amid the coronavirus pandemic.

In 2016, the royal great-grandkids had a special photo opportunity with the Queen for her 90th birthday. They were only five at that time and they were joined by Queen Elizabeth's two youngest grandkids -- Lady Louis and James, Viscount Severn. 

Meanwhile, the Cambridge children are in the direct line to throne as well thus they are the only great-grandchildren with royal titles. Archie, on the other hand, could have been given a royal title but his parents, Prince Harry and Meghan Markle, the Duke and Duchess of Sussex, declined.

They said that want to raise Archie in normal life that's different from the royals, according to a Sussex family friend and famous primatologist Dr. Jane Goodall. She said that when she commented on how Archie would have to learn to wave like the Queen, Prince Harry apparently said he will not grow up with such a life.