Question: Who is the paternal grandfather of Reginald I Of Guelders?

Knowledge 1: Reginald I of Guelders
Reginald I of Guelders (1255 – Monfort, October 9, 1326) was Count of Guelders from January 10, 1271 until his death.He was the son of Otto II, Count of Guelders and Philippe of Dammartin.<br>In 1276 he married Irmgard of Limburg, only daughter and heiress of Waleran IV, Duke of Limburg.In 1279 he became Duke of Limburg and when Irmgard died childless in 1283, he became the only ruler of the Duchy of Limburg.He lost this title after losing the Battle of Woeringen in 1288.In 1286 he remarried Margaret of Flanders (1272–1331), daughter of Guy, Count of Flanders from his second marriage, with Isabelle of Luxembourg.They had 5 children:Financially ruined after the Battle of Woeringen, Guelders came under the influence of his father-in-law, the Count of Flanders.<br> From 1318, he was replaced by his son, who imprisoned his father in 1320 in the Montfort Castle.Reginald I died here 6 years later. [SEP] Knowledge 2: Otto II, Count of Guelders
Otto II, Count of Guelders(Dutch:Otto II, Graaf van Gelre) was a nobleman from the 13th century.He was the son of Gerard III, Count of Guelders and Margaretha of Brabant.
Knowledge 1: Reginald I of Guelders
Reginald I of Guelders (1255 – Monfort, October 9, 1326) was Count of Guelders from January 10, 1271 until his death.He was the son of Otto II, Count of Guelders and Philippe of Dammartin.<br>In 1276 he married Irmgard of Limburg, only daughter and heiress of Waleran IV, Duke of Limburg.In 1279 he became Duke of Limburg and when Irmgard died childless in 1283, he became the only ruler of the Duchy of Limburg.He lost this title after losing the Battle of Woeringen in 1288.In 1286 he remarried Margaret of Flanders (1272–1331), daughter of Guy, Count of Flanders from his second marriage, with Isabelle of Luxembourg.They had 5 children:Financially ruined after the Battle of Woeringen, Guelders came under the influence of his father-in-law, the Count of Flanders.<br> From 1318, he was replaced by his son, who imprisoned his father in 1320 in the Montfort Castle.Reginald I died here 6 years later. [SEP] Knowledge 2: Otto I, Count of Guelders
Otto I of Guelders( 1150 – 1207) was a Count of Guelders and Zutphen from 1182 until his death in 1207.He was a son of Duke Hendrik of Guelders and Agnes of Arnstein.He married Richardis of Bavaria in 1184.Richardis was a daughter of Otto I Wittelsbach, Duke of Bavaria.
Knowledge 1: Reginald I of Guelders
Reginald I of Guelders (1255 – Monfort, October 9, 1326) was Count of Guelders from January 10, 1271 until his death.He was the son of Otto II, Count of Guelders and Philippe of Dammartin.<br>In 1276 he married Irmgard of Limburg, only daughter and heiress of Waleran IV, Duke of Limburg.In 1279 he became Duke of Limburg and when Irmgard died childless in 1283, he became the only ruler of the Duchy of Limburg.He lost this title after losing the Battle of Woeringen in 1288.In 1286 he remarried Margaret of Flanders (1272–1331), daughter of Guy, Count of Flanders from his second marriage, with Isabelle of Luxembourg.They had 5 children:Financially ruined after the Battle of Woeringen, Guelders came under the influence of his father-in-law, the Count of Flanders.<br> From 1318, he was replaced by his son, who imprisoned his father in 1320 in the Montfort Castle.Reginald I died here 6 years later. [SEP] Knowledge 2: Reginald III, Duke of Guelders
Reginald III of Guelders( or" Renaud", known as" The Fat")( 13 May 1333 – 4 December 1371) was Duke of Guelders and Count of Zutphen from 1343 to 1361, and again in 1371.He was the son of Reginald II of Guelders and of Eleanor of Woodstock, daughter of Edward II of England.With the death of his father in 1343, his mother held the regency until 1344.From 1350, his brother Edward asserted his rights and a quarrel of succession broke out between the two brothers until 1361.Reginald was overcome in Tiel and was imprisoned in the castle of Nijenbeek.There he became so large that he could not have left, even if the door had remained open—hence his appellation" The Fat".Edward died on 24 August 1371, having been mortally wounded in the Battle of Baesweiler, and Reginald was released( according to the legend, the walls had to be cut away so he could leave); he held the ducal throne for only a short period, dying a few months later.He was buried at Graefenthal Abbey.As he did not have a legitimate child, the succession passed to his sisters: Mathilde( also, Machteld), who was married to John II, Count of Blois, and Maria, wife of William II of Jülich and mother to William I of Guelders and Jülich, on whose behalf she claimed the throne of Guelders.The sisters and their respective followers( the" Heeckerens", from the party led by families of Van Heeckeren and their relatives, the Van Rechterens, supported Mathilde, while the faction known as the" Bronkhorsters" followed Maria) fought for the duchy of Guelders in the War of the Succession of Guelders.

Answer: Gerard III, Count of Guelders