There is evidence that some of Victoria's descendants did have mild porphyria (although some historians now think it could have been bi-polar disorder), most notably Princess Feodora of Saxe-Meiningen. This disease probably affected her grandfather, George III and this could give credence to Victoria's legitimate birth. There is more reliable documentation that one of her great-great-grandsons, Prince William of Gloucester, was diagnosed with the disease shortly before his death when his aircraft crashed during an air race. Concrete evidence on the origins of the disease and paternity of Victoria could be achieved with a DNA test of her or her parents' remains, but no such study has been sanctioned by the Royal Family.