James is fully styled as The Right Honourable Viscount Severn, and is more commonly referred to as a Lord, like his sister who is known as Lady Louise.
He does not have a HRH (His Royal Highness) title and was instead, alongside his older sister, given the last name of Mountbatten-Windsor.
Mountbatten-Windsor is the personal surname used by some of the male-line descendants of Queen Elizabeth II and Prince Philip, Duke of Edinburgh.
The name Windsor has been in the British Royal Family for a long time, but Mountbatten comes from Philip’s family.
