Tags
Kings and Queens of England, kings and queens of Scotland, kings and queens of the United Kingdom, Line of Succession, Louis Arthur Charles, Prince Louis of Cambridge, The Duchess of Cambridge, The Duke of Cambridge
The name of the Royal Baby: HRH Prince Louis Arthur Charles of Cambridge.
Both the Duke of Cambridge and Prince George of Cambridge have Louis among their names, as do other members of the Royal Family. This is the first member of the Royal Family to have Louis as a first name in British history.
Technically I do not count Lord Louis Mountbatten (Prince Louis of Battenberg), uncle of the Duke of Edinburgh who technically belonged to the House of Mountbatten a morganatic offshoot of the German House of Hesse and By Rhine.
Prince Louis of Cambridge is fifth in line to the throne of the United Kingdom of Great Britain and Northern Ireland.
European Royal History 
It makes sense of William’s ‘funny you should say that’ comment when someone suggested Alexander – a middle name of Prince George – as they were choosing the other middle name of Prince George! I do like the name Louis and prefer it to some on the other suggested names.