Charles, Count of Valois
Charles of Valois (12 March 1270 – 16 December 1325), the third son of Philip III of France and Isabella of Aragon, was a member of the House of Capet and founder of the House of Valois, whose rule over France would start in 1328.
Charles ruled several principalities.
He held in appanage the counties of Valois, Alençon and Perche.
Through his marriage to Margaret of Anjou, he became Count of Anjou and Maine.
Through his marriage to Catherine I, titular empress of the Latin Empire, he was titular Latin Emperor of Constantinople from 1301–1307, although he ruled from exile and only had authority over Crusader States in Greece.
The grandson of Louis IX of France, Charles of Valois was a son, brother, brother-in-law and son-in-law of kings or queens (of France, Navarre, England and Naples).
His descendants, the House of Valois, would become the royal house of France three years after his death, beginning with his son Philip VI of France.
Margaret of Valois, Countess of Blois
Margaret of Valois( 1295–1342) was a French noblewoman.
She was a daughter of Charles, Count of Valois, and his first wife, Margaret, Countess of Anjou.
She was also a sister of King Philip VI of France.
In 1310, she married Guy I, Count of Blois.
They had three children together:
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.
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.
Ermengarde-Gerberga of Anjou
Ermengarde- Gerberga of Anjou, also called Ermengarde of Anjou, was the Countess of Rennes, Regent of Brittany( 992–994) and also Countess of Angoulême.
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.
Serena Armstrong-Jones, Countess of Snowdon
Serena Alleyne Armstrong- Jones, Countess of Snowdon(" née" Stanhope; born 1 March 1970) is an Anglo- Irish aristocrat and the daughter- in- law of Princess Margaret, Countess of Snowdon, and a niece- by- marriage of Queen Elizabeth II and Prince Philip, Duke of Edinburgh.
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.
Joan of Valois, Countess of Hainaut
Joan of Valois( c. 1294 – 7 March 1342) was a Countess consort of Hainaut, Holland, and Zeeland.
She was the second eldest daughter of the French prince Charles, Count of Valois, and his first wife, Margaret, Countess of Anjou.
As the sister of King Philip VI of France and the mother- in- law of Edward III, she was ideally placed to act as mediator between them.
Margaret, Countess of Anjou
Margaret, Countess of Anjou (1272 – 31 December 1299) was Countess of Anjou and Maine in her own right and Countess of Valois, Alençon, Chartres and Perche by marriage.
Margaret's father was King Charles II of Naples, whilst her husband was Charles of Valois, and her older brother was Saint Louis of Toulouse; her nephew was Charles I of Hungary.

Question: Who is the mother-in-law of Margaret, Countess Of Anjou?
Answer: Isabella of Aragon