Elizabeth Lyon , Countess of Strathmore and Kinghorne , was an English noblewoman and the wife of Scottish peer John Lyon, 4th Earl of Strathmore and Kinghorne. Born to Lady Elizabeth Butler and Philip Stanhope, 2nd Earl of Chesterfield, her paternity was in doubt. It is possible that her actual father was James, Duke of York, who would in 1685 ascend the throne as King James II of England.
Lady Elizabeth was born in May 1663 at Bretby, Derbyshire, England, the daughter of Philip Stanhope, 2nd Earl of Chesterfield and Lady Elizabeth Butler, eldest daughter of James Butler, 1st Duke of Ormonde. Her paternity was in doubt as despite her putative fathers own licentious conduct, having been the lover of the notorious Barbara Villiers, mistress of King Charles II of England, he believed that Elizabeth was not his daughter. Prior to her birth, Samuel Pepys alleged that Elizabeths mother, tired of her husbands neglect of her in his pursuit of Barbara Villiers, had had affairs with both James Hamilton and James, Duke of York, who would later rule as King James II of England. In fact, she was caught in flagrante with the latter. It is possible, although it cannot be firmly established, that Elizabeth was in fact an illegitimate child of the Duke of York. Historian Antonia Fraser describes Elizabeths mother as having been one of his mistresses.
Source: Wikipedia