Matilda of Brabant, Countess of Artois
Matilda of Brabant (14 June 1224 – 29 September 1288) was the eldest daughter of Henry II, Duke of Brabant and his first wife Marie of Hohenstaufen.
Hugh IV, Count of Saint-Pol
Hugh IV of Saint- Pol( died March 1205 in Constantinople) from the House of Campdavaine, son of Anselm of Saint- Pol, was Count of Saint- Pol from 1174 to his death, and lord of Demotika( Didymoteicho) in Thrace in 1204 – 05.
He participated in the Third and Fourth Crusades.
Guy III, Count of Saint-Pol
Guy III of Châtillon, Count of Saint-Pol (died 1289) was a French nobleman, and was a younger son of Hugh I, Count of Blois and Mary, Countess of Blois.
While his elder brother John I of Châtillon succeeded to their mother's County of Blois, Guy was given their father's county of Saint-Pol-sur-Ternoise at his death in 1248.
On January 16, 1255, he married Matilda of Brabant, Countess of Artois, daughter of Henry II, Duke of Brabant and Marie of Hohenstaufen, and thereafter was a supporter of his brother-in-law Henry III against Guelders.
They had:
He joined the Eighth Crusade (1270) and the ill-fated Crusade of Aragón of Philip III of France.
John, Count of Saint-Pol
John of Saint- Pol( died 1344) was Count of Saint- Pol between 1317 and 1344.
He was the eldest son of Guy IV, Count of Saint- Pol and Marie of Brittany.
He married in 1319 with Joanna, daughter of John I of Fiennes, and had 2 children:
Guy IV, Count of Saint-Pol
Guy IV of Châtillon, Count of Saint Pol( – April 6, 1317) was a French nobleman.
He was the son of Guy III, Count of Saint- Pol and Matilda of Brabant.
In 1292, he married Marie of Brittany, daughter of John II, Duke of Brittany and Beatrice of England.
They had eight children:
He held the office of Grand Butler of France.
He was placed in joint command( with Robert VI of Auvergne) of one of the two reserve" battles" of the French troops at the Battle of the Golden Spurs.
He was able to escape when the French were routed by the Flemings, but his brother Jacques and many of his relatives were killed.
John I of Brienne, Count of Eu
John I of Brienne( died 12 June 1294) was the son of Alphonso of Brienne and Marie de Lusigan.
His mother was the heiress of Eu, Seine- Maritime, and he succeeded his father as Count of Eu in 1270.
He married Beatrice, the daughter of Guy III, Count of Saint- Pol.
They had: John died at Clermont- en- Beauvaisis in 1294.
Joan, Countess of Ligny
Joan, Countess of Saint- Pol and Ligny( d. 18 September 1430, Avignon), called the Demoiselle de Luxembourg, was the daughter of Guy of Luxembourg, Count of Ligny and Mahaut of Châtillon, Countess of Saint- Pol.
At the death of Philip I, Duke of Brabant, she was his nearest living relative on the Saint- Pol side and inherited Saint- Pol and Ligny upon his death on 14 August 1430.
She was living at the time at Beaurevoir, which belonged to her favourite nephew John.
At this time, John held Joan of Arc, whom he had captured, as a prisoner.
The Demoiselle de Luxembourg showed kindness to her and pleaded with her nephew not to sell Joan to the English.
The Demoiselle died shortly thereafter; her fiefs were divided between her senior nephew, the Count of Brienne, who received Saint- Pol, and John, her favourite, who received Ligny.
The Demoiselle is a character in Philippa Gregory's 2011 historical novel" The Lady of the Rivers", which centres on her great- niece Jacquetta of Luxembourg.
Hugh II, Count of Blois
Hugh II of Châtillon( died 1307), son of Guy III, Count of Saint- Pol, and Matilda of Brabant, was count of St Pol 1289 – 1292 and count of Blois 1292 – 1307.
He married c. 1287 Beatrix of Dampierre, daughter of Guy of Flanders and Isabelle of Luxembourg.
They had two children:
Walter III of Châtillon
Walter III of Châtillon( 1166- 1219), also known as Gaucher III of Châtillon, was a French nobleman.
He was a son of Guy II of Châtillon and Adèle of Dreux ..
His brother was Guy III, lord of Chatillon.
In 1196 he married Elisabeth of Saint- Pol, daughter of Hugo IV, Count of Saint- Pol and in 1205, he succeeded his father- in- law as count of Saint- Pol.
Walter and Elisabeth had:
Anthony I, Count of Ligny
Anthony I, Count of Ligny( 1450 – 1519) was the youngest son of Louis de Luxembourg, Count of Saint- Pol and his wife, Jeanne de Bar, Countess of Marle and Soissons.
In 1482, he inherited the County of Brienne from his brother Peter II, Count of Saint- Pol.
After the death of Charles of Bourbon in 1510, Anthony inherited the County of Ligny, which thereby fell back to the House of Luxemburg.

Question: What is the date of death of Guy Iii, Count Of Saint-Pol's wife?
Answer: 29 September 1288