Through her mother, Mary was descended from Charles Beauclerk, 1st Duke of St Albans (1670–1726), illegitimate son of King Charles II of England and his mistress Nell Gwynn.
Mary's lineage traced back to Charles Beauclerk, 1st Duke of St Albans (1670–1726), an illegitimate child of King Charles II of England and his mistress, Nell Gwynn.