Baldwin V, Count of Flanders
Baldwin V of Flanders( c. 1012 – 1 September 1067) was Count of Flanders from 1035 until his death.
He was the son of Baldwin IV, Count of Flanders, who died in 1035.
Margaret I, Countess of Burgundy
Margaret I( 1310 – 9 May 1382), was a ruling Countess Palatine of Burgundy and Artois from 1361 and 1382.
She was also countess of Flanders, Nevers and Rethel by marriage to Louis I, Count of Flanders, and regent of Flanders during the minority of her son Louis II, Count of Flanders in 1346.
William II, Count of Flanders
William III (1224 – 6 June 1251) was the lord of Dampierre from 1231 and count of Flanders from 1247 until his death.
He was the son of William II of Dampierre and Margaret II of Flanders.
Margaret inherited Flanders and Hainault in 1244 and immediately the War of the Succession of Flanders and Hainault began between William and his brothers, the Dampierre claimants, and the children of Margaret's first marriage to Bouchard of Avesnes.
Margaret favoured William and declared him her heir.
In 1246, Louis IX of France intervened to arbitrate the conflict and declared Flanders to William and Hainault to John I of Avesnes.
Margaret officially invested William as count in 1247.
In November of that year, William married Beatrice of Brabant, daughter of Henry II, Duke of Brabant and Marie of Hohenstaufen.
They had no children.
Meanwhile, the fight continued over Namur between the Dampierres and the Avesnes.
On 19 May 1250, peace was signed.
On 6 June the next year, William died at a tournament in Trazegnies.
The war began anew with Guy, William's younger brother, taking up Flanders and the Dampierre claim.
Beatrice of Brabant
Beatrice of Brabant( 1225 – 11 November 1288), was a Landgravine consort of Thüringia and a Countess consort of Flanders, married to Henry Raspe, Landgrave of Thuringia, and later to William II, Count of Flanders.
She was the daughter of Henry II, Duke of Brabant, and Marie of Hohenstaufen.
She had no children.
Arnulf I, Count of Flanders
Arnulf of Flanders( c. 890 – 27 March 965), called the Great, was the first Count of Flanders.
Henry of Flanders
Henry( 1176? – 11 June 1216) was the second emperor of the Latin Empire of Constantinople.
He was a younger son of Baldwin V, Count of Hainaut( later Baldwin VIII, count of Flanders), and Margaret I of Flanders, sister of Philip of Alsace, count of Flanders.
Richilde, Countess of Hainaut
Richilde, Countess of Mons and Hainaut( – 15 March 1086), was a ruling countess of Hainaut from c. 1050 until 1076, in co-regency with her husband Baldwin VI, Count of Flanders and son Baldwin II, Count of Hainaut.
She was also countess consort of Flanders by marriage to Baldwin VI, Count of Flanders.
She served as regent of Flanders during the minority of her son Arnulf III, Count of Flanders in 1070- 1071.
William II, Count of Eu
William II, Count of Eu, feudal baron of Hastings( d. circa 1095) was a first generation Anglo- Norman nobleman, Count of Eu and rebel.
Margaret of Clermont
Margaret of Clermont( 1104/05 – after 1145) was a countess of Flanders and Saint- Pol. Margaret's parents were Renaud II, Count of Clermont- en- Beauvaisis, and Adelaide, Countess of Vermandois.
Margaret was first married to Charles I, Count of Flanders.
The marriage was brief and childless.
Later, cca. 1128, Margaret married Hugh II, Count of Saint- Pol; they had two sons.
Her third husband was Baldwin of Encre.
They had one daughter.
William II of Dampierre
William II (1196 – 3 September 1231) was the lord of Dampierre from 1216 until his death.
He was the son of Guy II, constable of Champagne, and Mathilde of Bourbon.
His brother, Archambaud VIII, inherited Bourbon, and William inherited Dampierre.
He married Margaret II, Countess of Flanders and Hainault, in 1223 and was thus regent of Flanders until his death as "Willem I" (or "Guillaume I").
In 1226 William and Margaret founded a Cistercian nunnery at Saint-Dizier.
Their sons William III and John continued to confirm and patronize the nunnery during their lives, including William II's burial there in 1231.
William and Margaret founded more Cisterian nunneries throughout the county of Flanders, including Flines Abbey.
He had four children (three sons) by Margaret and the eldest took part in the War of the Succession of Flanders and Hainault:

Question: Who is the mother of William Ii, Count Of Flanders?