Complex sentence: The grave does not actually exist; the headstone for Capt. John Miller was only brought to the cemetery for the movie, no real Capt. John Miller ever lived-the Private Ryan story is based upon the story of the Niland Brothers.
Split into simpler sentences: The grave does not actually exist; the headstone for Capt. John Miller was only brought to the cemetery for the movie. The Capt. John Miller potrayed in the movie never existed-the Private Ryan story is based upon the story of the Niland Brothers.