Peter, Duke of Coimbra
Infante D. Pedro, Duke of Coimbra , (9 December 1392 – 20 May 1449) was a Portuguese "infante" (prince) of the House of Aviz, son of King John I of Portugal and his wife Philippa of Lancaster, daughter of John of Gaunt.
In Portugal, he is better known as Infante D. Pedro das Sete Partidas [do Mundo], "of the Seven Parts [of the World]" because of his travels.
Possibly the best-travelled prince of his time
, he was regent between 1439 and 1448.
He was also 1st
Lord of Montemor-o-Velho, Aveiro, Tentúgal, Cernache, Pereira, Condeixa and Lousã.
Isabella of Urgell, Duchess of Coimbra
Isabella of Urgell, Duchess of Coimbra (Spanish: "Isabel")
(12 March 1409 – 17 September 1459) was a Catalan noblewoman of the Urgell branch of the House of Aragon.
She was the wife of Infante Peter, Duke of Coimbra.
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.
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.
Philippa of Coimbra
Infanta Philippa of Coimbra( 1437 – 1497) was the youngest child of Infante Peter, Duke of Coimbra, and Isabella of Aragon, Countess of Urgell.
She became a nun in the Convent of Odivelas where she died in 1497.
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.
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.
John, Prince of Antioch
John, Prince of Antioch( 1431 – 1457), was the second son of Infante Peter, Duke of Coimbra, and Isabella of Urgell, Duchess of Coimbra.
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.
Beatrice of Coimbra
Infanta Beatrice of Coimbra( 1435 – 1462) was the 5th child of Infante Peter, Duke of Coimbra, and Isabella of Urgell.
After the battle of Alfarrobeira, where her father's army was defeated by the Portuguese royal army, she left the country and took refuge in Burgundy, under her aunt ’s protection: Isabella of Portugal was married to Duke Philip III the Good.
In 1453, Beatrice married Adolph of Cleves, Lord of Ravenstein, nephew of the Duke Philip III the Good.
They had issue:
She died in Bruges of suspected poisoning in 1462.

Question: Who is the mother-in-law of Isabella Of Urgell, Duchess Of Coimbra?
Answer: Philippa of Lancaster