Question:  Katherine Stanhope, Countess of Chesterfield was the governess and confidante of this Princess who was married to who 

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Philip Stanhope (diplomat): Philip Stanhope (2 May 1732 – 16 November 1768) was the illegitimate son of Philip Stanhope, 4th Earl of Chesterfield to whom the famous "Letters to His Son" were addressed.  His mother was a French governess, Madelina Elizabeth du Bouchet.

Baron Wotton: Baron Wotton was a title that was created twice in the Peerage of England.  The first creation came in 1603 for Sir Edward Wotton, of Boughton Place, Boughton Malherbe, Kent, a descendant of Nicholas Wotton (d. 1448), twice Lord Mayor of London, who married Joan Corbye, heiress of Boughton Malherbe and settled at Boughton Place.  Edward, in 1594 followed several of his forebears as High Sheriff of Kent and served as Ambassador to Queen Elizabeth I.  After the death of his son and heir, the second Baron, in 1630, without male issue, the barony became extinct.  His estate passed to his eldest daughter the Honourable Katherine, who firstly married Henry Stanhope, Lord Stanhope.  She was created Countess of Chesterfield for life on his death and later married Jehan van Kerkhoven.  The title was revived for her son by her second husband, Charles Henry, who also created Earl of Bellomont in 1680.  For more information on the second creation, which became extinct in 1683, see Earl of Bellomont.

Elizabeth Stanhope, Countess of Chesterfield: Elizabeth Stanhope, Countess of Chesterfield (29 June 1640 – July 1665) was the second wife of Philip Stanhope, 2nd Earl of Chesterfield, and the eldest daughter of James Butler, 1st Duke of Ormonde and Lady Elizabeth Preston.

Baron Stanhope: Baron Stanhope, of Harrington in the County of Northampton, was a title in the Peerage of England.  It was created on 2 May 1605 for Sir John Stanhope, Vice-Chamberlain of the Household between 1602 and 1616.  He was the son of Sir Michael Stanhope and the brother of Sir Thomas Stanhope, ancestor of the Earls of Chesterfield, the Earls of Harrington and the Earls Stanhope.  Lord Stanhope was succeeded by his son, Charles, the second Baron.  The title became extinct on his death in 1675.

Katherine Stanhope, Countess of Chesterfield: Katherine Stanhope, Countess of Chesterfield (1609–1667) was the governess and confidante of Mary, Princess Royal and Princess of Orange, and was the first woman to hold the office of Postmaster General of England.

Mary, Princess Royal and Princess of Orange: Mary, Princess Royal (Mary Henrietta; 4 November 1631 – 24 December 1660) was Princess of Orange and Countess of Nassau by marriage to Prince William II, and co-regent for her son during his minority as Sovereign Prince of Orange from 1651 to 1660.

Philip Stanhope, 4th Earl of Chesterfield: Philip Dormer Stanhope, 4th Earl of Chesterfield, {'1': ", '2': ", '3': ", '4': "} (22 September 169424 March 1773) was a British statesman, man of letters, and wit.  He was born in London to Philip Stanhope, 3rd Earl of Chesterfield, and Lady Elizabeth Savile, and known as Lord Stanhope until the death of his father, in 1726.  Educated at Trinity Hall, Cambridge, he subsequently embarked on the Grand Tour of the Continent, to complete his education as a nobleman, by exposure to the cultural legacies of Classical antiquity and the Renaissance, and to become acquainted with his aristocratic counterparts and the polite society of Continental Europe.

Earl Stanhope: Earl Stanhope (pronounced Stannup) was a title in the Peerage of Great Britain.  It was created in 1718 for James Stanhope, 1st Viscount Stanhope, the principal minister of King George I, with remainder to the heirs male of his body.  Stanhope was the son of the Hon. Alexander Stanhope, fifth and youngest son of Philip Stanhope, 1st Earl of Chesterfield.  He had already been created Viscount Stanhope, of Mahón in the Island of Minorca, and Baron Stanhope, of Elvaston in the County of Derby, in 1717, with remainder, failing heirs male of his body, to his second cousin John Stanhope of Elvaston (who was the father of William Stanhope, 1st Earl of Harrington) and the heirs male of his body.  These titles were also in the Peerage of Great Britain.

Earl of Chesterfield: Earl of Chesterfield, in the County of Derby, was a title in the Peerage of England.  It was created in 1628 for Philip Stanhope, 1st Baron Stanhope.  He had already been created Baron Stanhope, of Shelford in the County of Nottingham, in 1616, also in the Peerage of England.  Stanhope's youngest son the Hon. Alexander Stanhope was the father of James Stanhope, 1st Earl Stanhope while his half-brother Sir John Stanhope of Elvaston was the great-grandfather of William Stanhope, 1st Earl of Harrington.

Stanhope Aspinwall: Stanhope Aspinwall (born 5 July 1713 in Liverpool, England and died on 17 January 1771) was a British diplomat.  He was born to Richard Aspinwall and his wife Elizabeth Stanhope, the great granddaughter of Philip Stanhope, 1st Earl of Chesterfield, the granddaughter of Arthur Stanhope and daughter of Charles Stanhope.

Supporting paragraphs: Katherine Stanhope, Countess of Chesterfield Mary, Princess Royal and Princess of Orange
Answer: Prince William II