"The baby will be known as His Royal HighnessPrince Louis of Cambridge". As they do every year, the royals marked the day in private, but through the years, William and Kate have had public engagements, or the Duchess has been expecting.
Bookmakers had Arthur as the favourite initially, with James and Philip also popular.
Prince George, whose first name comes from Queen Elizabeth's father, King George VI, shares the middle name Louis with his baby brother, as well as the middle name Alexander, a masculine version of his great grandmother, Queen Elizabeth's, middle name. The name also bears a special meaning to infant's grandfather, Prince Charles, whose beloved uncle and mentor named Earl Louis Mountbatten was assassinated by the IRA back in 1979. Louis is also part of William's full name William Arthur Phillip Louis.
Australian High Commissioner Alexander Downer told Will that the baby might suit "Prince Alexander" and Will replied: "Funny you should say that".
The same logic applies to Kate, who married into the royal family, and to avoid confusion was given the title Her Royal Highness Kate, The Duchess Of Cambridge, Countess Of Strathearn and Lady Carrickfergus. The baby weighs 8lbs 7oz.
The birth has also brought some speculation that the Duke of York may remarry his former wife, Sarah, Duchess of York.
Big brother and sister Prince George and Princess Charlotte got to meet their little brother while he was still at hospital, in a display of cuteness that melted hearts all over the world.
Speaking of the monarch, she's "delighted" to have another great-grandchild.
The caption read, "Seven years ago today-thank you for all the lovely messages on The Duke and Duchess of Cambridge's wedding anniversary".
MEET the other Louis Charles Cambridge - a 21-year-old royalty-mad nurse whose mum is Catherine and grandmother is Victoria. Her middle names, Elizabeth and Diana, have straightforward sources: her great-grandmother Queen Elizabeth, and her late grandmother Princess Diana, Prince William's mother. The outlet cites Andrew Morton's Princess Diana book, where Morton reported that Diana's reaction to seeing Charles so grief-stricken at the funeral is what ultimately brought her and Charles together.