John II of Brienne, Count of Eu
John II of Brienne( died 11 July 1302 in Kortrijk) was the son of John I of Brienne, Count of Eu and Beatrice of Saint- Pol.
He succeeded his father as Count of Eu in 1294.
He married Jeanne, Countess of Guînes( d. 1331/ 32), the daughter and heir of Baldwin IV, Count of Guînes.
They had two children: John was killed at the Battle of the Golden Spurs.
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.
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.
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.
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.
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.
Alice of Namur
Alice of Namur( died July 1169 at Valenciennes) was the daughter of Godfrey I, Count of Namur and Ermesinde, Countess of Luxembourg and Longwy the daughter of Conrad I of Luxembourg.
Her father married her off to Baldwin IV, Count of Hainault around 1130.
Gislebert of Mons described her as having" a graceful body and a beautiful face".
Her son was the heir of Namur when her brother Henry IV of Luxembourg died in 1196.
Her children with Baldwin IV of Hainaut were:
She was buried inside Saint Waltrude Collegiate Church.
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.
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.
Alix de Montmorency
Alix de Montmorency( died 24 February 1220/ 1221) was a French noblewoman.
Her parents were Bouchard V de Montmorency and Laurette, daughter of Baldwin IV, Count of Hainaut and Alice of Namur.

Question: Who is Baldwin Iv, Count Of Hainaut's paternal grandfather?
Answer: Baldwin II, Count of Hainaut