Prince William and Kate Middleton Reveal Their Royal Baby Boy’s Name If you bet Prince Louis as the name of William and Kate’s third child, collect your prize. A statement from Kensington Palace on Friday morning reveals the full name of the royal baby. Louis Arthur Charles will be known as His Royal Highness Prince Louis of Cambridge. The name comes from a long linage of royal names. Louis is a part of William’s full name, William Arthur Philip Louis, and Prince George’s full name of George Alexander Louis. Charles and Arthur hold a special meaning as well. The baby’s grandfather is named Charles and Arthur is a family tradition dating back to Queen Victoria’s favorite child. Do you know how your name came to be picked?