The Queen's youngest grandchildren, Lady Louise Windsor and James, Viscount Severn, are the only male-line grandchildren not to hold Prince or Princess titles - but that could change.
Lady Louise Windsor, who turned 18 last year, wasn't well known during her childhood, however has made a number of public appearances following the death of Prince Philip.
READ MORE - Amazon shoppers say £2 migraine and headache product is 'better than tablets'