Question: Who is Reginar Iv, Count Of Mons's paternal grandfather?

Knowledge 1: 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. [SEP] Knowledge 2: Reginar III, Count of Hainaut
Reginar III (c. 920 – 973) was a Count of Hainaut from approximately 940 until his exile in 958.He was the son of Reginar II, Count of Hainaut.He took part in the rebellion of his uncle Gilbert, Duke of Lorraine.When Gilbert was killed in 939, Regnier had to pledge fealty to King Otto the Great.He then allied himself with King Louis IV of France, but King Otto sent duke Hermann of Swabia to quell the rebels in 944.Otto appointed Conrad the Red as duke of Lotharingia, who tried to diminish the power of Reginar.However, when Conrad rose against Otto, Reginar supported him.In an anarchic situation, Reginar appropriated the dowry of Gerberga of Saxony, Otto's sister and mother of the French king, and also church property.In 953, Bruno, Archbishop of Cologne, who had also been appointed duke of Lotharingia, restored order and defeated Reginar.As Reginar refused to submit, he was exiled to Bohemia, where he died.
Knowledge 1: 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. [SEP] Knowledge 2: Herman, Count of Hainaut
Herman (died 3 July 1049), Count of Mons and Hainaut, son of Reginar V, Count of Mons, and Mathilde of Verdun, daughter of Herman, Count of Verdun.As the Count of Mons, a title inherited from his father, he allied with Godfrey the Bearded, Duke of Lorraine, and Baldwin V, Count of Flanders, against Emperor Henry III.This won the countship of Valenciennes, completing the reconstruction of Hainaut.His wife, who preferred an alliance with the emperor, attempted to get Herman to imprison Wazo, Bishop of Liège, but he refused.In 1040, Herman married Richilde, whose origins are uncertain.Herman and Richilde had two children:
After the death of Herman, Richilde married the son of Baldwin V, who arranged for Herman's children to be disinherited.Richilde's new husband, Baldwin VI the Good, became Herman's successor and count of a unified Hainaut/Flanders.Because of this passage of Hainaut to her new husband and children, Richilde is sometimes wrongly portrayed as daughter of Reginar V.Her true parentage is subject to speculation, one theory being that she was the daughter of a count of Eguisheim and Dagsbourg.
Knowledge 1: Reginar III, Count of Hainaut
Reginar III (c. 920 – 973) was a Count of Hainaut from approximately 940 until his exile in 958.He was the son of Reginar II, Count of Hainaut.He took part in the rebellion of his uncle Gilbert, Duke of Lorraine.When Gilbert was killed in 939, Regnier had to pledge fealty to King Otto the Great.He then allied himself with King Louis IV of France, but King Otto sent duke Hermann of Swabia to quell the rebels in 944.Otto appointed Conrad the Red as duke of Lotharingia, who tried to diminish the power of Reginar.However, when Conrad rose against Otto, Reginar supported him.In an anarchic situation, Reginar appropriated the dowry of Gerberga of Saxony, Otto's sister and mother of the French king, and also church property.In 953, Bruno, Archbishop of Cologne, who had also been appointed duke of Lotharingia, restored order and defeated Reginar.As Reginar refused to submit, he was exiled to Bohemia, where he died. [SEP] Knowledge 2: Herman, Count of Hainaut
Herman (died 3 July 1049), Count of Mons and Hainaut, son of Reginar V, Count of Mons, and Mathilde of Verdun, daughter of Herman, Count of Verdun.As the Count of Mons, a title inherited from his father, he allied with Godfrey the Bearded, Duke of Lorraine, and Baldwin V, Count of Flanders, against Emperor Henry III.This won the countship of Valenciennes, completing the reconstruction of Hainaut.His wife, who preferred an alliance with the emperor, attempted to get Herman to imprison Wazo, Bishop of Liège, but he refused.In 1040, Herman married Richilde, whose origins are uncertain.Herman and Richilde had two children:
After the death of Herman, Richilde married the son of Baldwin V, who arranged for Herman's children to be disinherited.Richilde's new husband, Baldwin VI the Good, became Herman's successor and count of a unified Hainaut/Flanders.Because of this passage of Hainaut to her new husband and children, Richilde is sometimes wrongly portrayed as daughter of Reginar V.Her true parentage is subject to speculation, one theory being that she was the daughter of a count of Eguisheim and Dagsbourg.

Answer: Reginar II, Count of Hainaut