Eldon Howard
Eldon Howard was a British screenwriter.
She was the mother- in- law of Edward J. Danziger and wrote a number of the screenplays for films by his company Danziger Productions.
Priscilla Pointer
Priscilla Marie Pointer( born May 18, 1924) is an American stage, film and television character actress.
She began her career in the theater, including productions on Broadway.
Later, Pointer moved to Hollywood to act in films and on television.
She is the mother of Amy Irving, therefore making her the former mother- in- law of filmmakers Steven Spielberg and Bruno Barreto and the mother- in- law of documentary filmmaker Kenneth Bowser, Jr.
Maria Thins
Maria Thins( c. 1593 – 27 December 1680) was the mother- in- law of Johannes Vermeer and a member of the Gouda Thins family.
Mary FitzRoy, Duchess of Richmond and Somerset
Mary FitzRoy, Duchess of Richmond and Somerset( Howard; 1519 – 7 December 1557), born Lady Mary Howard, was the only daughter- in- law of King Henry VIII of England, being the wife of his only acknowledged illegitimate son, Henry FitzRoy, 1st Duke of Richmond and Somerset.
Marian Shields Robinson
Marian Lois Robinson( née Shields; born July 29, 1937) is the mother of Michelle Obama, former First Lady of the United States, and Craig Robinson, a basketball executive, and the mother- in- law of former U.S. President Barack Obama.
Isabella FitzRoy, Duchess of Grafton
Isabella Bennet FitzRoy, Duchess of Grafton and later 2nd Countess of Arlington" suo jure"( c. 1668 – 7 February 1723), was a British peer and heiress.
Anne FitzPatrick, Countess of Upper Ossory
Anne FitzPatrick, Countess of Upper Ossory( née Liddell, also known as Anne FitzRoy, Duchess of Grafton; c. 1737 – 1804) was an English noblewoman and the first wife of Augustus FitzRoy, 3rd Duke of Grafton.
Grafton divorced her while serving as Prime Minister.
She was a noted correspondent of Horace Walpole.
Fortune FitzRoy, Duchess of Grafton
Ann Fortune FitzRoy, Dowager Duchess of Grafton, (née Smith; 24 February 1920), is the widow of Hugh FitzRoy, 11th Duke of Grafton.
She has been Mistress of the Robes since 1967.
Doria Ragland
Doria L. Ragland( born September 2, 1956) is the mother of Meghan, Duchess of Sussex, the mother- in- law of Prince Harry, and the maternal grandmother of Archie Mountbatten- Windsor, who is seventh in line to the British throne.
She is a former makeup artist, business owner, yoga instructor, and former social worker who worked in the mental health sector from 2015 to 2018.
Hugh FitzRoy, 11th Duke of Grafton
Hugh Denis Charles FitzRoy, 11th Duke of Grafton (3 April 1919 – 7 April 2011) was the son of Charles FitzRoy, 10th Duke of Grafton, and his first wife Lady Doreen Maria Josepha Sydney Buxton, second daughter of Sydney Buxton, 1st Earl Buxton.
He was known from 1936 to 1970 as the Earl of Euston.

Question: Who is the mother-in-law of Fortune Fitzroy, Duchess Of Grafton?
Answer: Lady Doreen Maria Josepha Sydney Buxton