Getty The Duke and Duchess of Cambridge have called their third child Louis Arthur Charles ? and royal experts say it's a nod to relatives, past and present. One obvious link is with Prince Louis' grandfather, Prince Charles, while the name may also be a tribute to Louis Mountbatten, Prince Philip's uncle and mentor. The baby is fifth in line to the throne, bumping Prince Harry into sixth place. Prince William and Kate Middleton have called their third child Louis Arthur Charles ? and it is likely to be a nod to the young Prince's relatives, past and present.