The birth of her baby girl follows Eugenie’s sons August and Ernest, but where does the new baby sit in line for the British throne? Prince William, Prince of WalesPrince William, 44, is first in line to the British throne after his father became king. open image in gallery Prince William, 44, is first in line to the British throne ( Getty )2. The Princess RoyalThe Princess Royal, 75, also known as Princess Anne, is the 19th in line to the throne. open image in gallery Princess Anne, is the 19th in line to the throne ( Getty )20.