Van wie was Mary Day Beauclerk?

George Richard St John, 3rd Viscount Bolingbroke (5 March 1761 – 11 December 1824), styled The Honourable George St John from his birth until 1787, was a British politician. He became famous in his own lifetime for embarking on an extra-marital relationship with his own half-sister, Mary Beauclerk (his mother's daughter by her second marriage), that produced four sons. The two lovers had to leave England and live on the continent for a time.