Otto II, Count of Duras
Count Otto of Duras( d. 1147) was a Count of Duras, and" advocatus" of the Abbey of St Truiden.
Duras and St Truiden are in the modern province of Belgian Limburg.
His parents were Count Giselbert of Duras and his wife Gertrud.
Otto married Berthe of Valenciennes, daughter of Yolande of Guelders, daughter of Gerard I, Count of Guelders.
Yolande was first married to Baldwin III, Count of Hainaut, and was mother to Baldwin IV, Count of Hainaut.
Yolande was granddaughter of Albert III, Count of Namur, a family with strong relations with Otto ’s father.
Otto and Berthe are thought to have had one child who survived to adulthood, Otto's successor:
In fact, the relationship with Countess Juliane depends upon the meaning of the Latin word" gener", used in one document to describe the relationship between Otto and Juliane's husband Count Godfried.
This could mean" son- in- law" or" brother- in- law".
Wolters for example identified Juliane as Otto's sister, but this seems unlikely given the succession of the Counts of Duras.
Juliane and Godfried had five children, the eldest of which was Gilles, Count of Montaigu, Duras, and Clermont, who married Lauretta, daughter of Louis I, Count of Loon.
Their third son Conan was also Count of Duras.
None of Juliane's sons had male heirs, and the family inheritance split up after their deaths.
Baldwin III, Count of Hainaut
Baldwin III (1088–1120) was count of Hainaut from 1098 to his death.
He was son of Baldwin II, Count of Hainaut, and Ida of Louvain.
Reginar IV, Count of Mons
Reginar IV, Count of Mons( c. 950–1013) was the son of Reginar III, Count of Hainaut.
Lambert I of Leuven was his brother.
Manasses de Ramerupt
Manasses( died after 4 February 1031), son of Hilduin III, Count of Montdidier.
He was often mistaken for his uncle Manasses, Count of Dammartin.
Manasses married Beatrix of Hainaut, daughter of Reginar IV, Count of Mons, and Hedwig, daughter of Hugh Capet, widow of Ebles I, Count of Roucy.
They had three children:
No further information could be found on the descendants of Manasses.
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.
Baldwin IV, Count of Hainaut
Baldwin IV( 1108 – 8 November 1171) was count of Hainaut from 1120 to his death.
He was the son of Baldwin III, Count of Hainaut, and Yolande de Wassenberg.
Mary of Avesnes
Marie of Hainaut( 1280–1354) was the daughter of John II, Count of Holland and Philippa of Luxembourg, her brother was William I, Count of Hainaut.
Baldwin II, Count of Hainaut
Baldwin II of Mons (1056–1098?) was count of Hainaut from 1071 to his death.
He was the younger son of Baldwin VI, Count of Flanders and Richilde, Countess of Mons and Hainaut.
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.
William I, Duke of Bavaria
William I, Duke of Bavaria- Straubing( Frankfurt am Main, 12 May 1330 – 15 April 1389, Le Quesnoy), was the second son of Emperor Louis IV and Margaret II of Hainaut.
He was also known as William V, Count of Holland, as William III, Count of Hainaut and as William IV, Count of Zeeland.

Question: Who is the paternal grandfather of Baldwin Iii, Count Of Hainaut?
Answer: Baldwin VI, Count of Flanders