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.
Reginald of Piperno
Reginald of Piperno( or Reginald of Priverno) was an Italian Dominican, theologian and companion of St. Thomas Aquinas.
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.
Eleanor of Woodstock
Eleanor of Woodstock( 18 June 1318 – 22 April 1355) was an English princess and Duchess consort of Guelders by marriage.
She was regent of Guelders as the guardian of her minor son from 1343 until 1344.
Eleanor was born at Woodstock Palace in Oxfordshire to King Edward II of England and his queen Isabella of France.
She was a younger sister of Edward III of England and the second wife of Reginald II of Guelders," the Black".
Eleanor's maternal grandfather was King Philip the Fair of France.
Maria, Duchess of Guelders
Marie of Guelders( † May 12, 1405) was one of two pretenders to the title of Duchess of Guelders and Countess of Zutphen on behalf of her son during the War of the Guelderian Succession from 1371 to 1379.
The war began after the deaths of her brothers, Reginald III of Guelders and Edward of Guelders.
Edward died from wounds received at the Battle of Baesweiler, and Reginald, who was known as the fat, died months later.
Succession was also claimed by Marie's sister, Mathilda, whose side was called the" Heeckerens" and were led by Frederik van Heeckeren van der Eze( 1320- 1386).
Her party was called the" Bronckhorsters" and was led by Gijsbert V van Bronckhorst( 1328- 1356).
Upon victory of her party, the title of Duke of Guelders went to her son, William.
Marie was daughter of Reginald II, Duke of Guelders and Sophie Berthout, lady of Malines.
On December 25, 1362, she married William II, Duke of Jülich( † 1393).
They had three children:
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
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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.
Gerard III, Count of Guelders
Gerard III of Guelders( 1185 – 22 October 1229) was the Count of Guelders and Zutphen from 1207 until his death in 1229.
He was a son of Count Otto I of Guelders, and is sometimes called Gerard IV or Gerard V.
He married Margaretha of Brabant, the daughter of Duke Hendrik I of Brabant, in 1206.
Catherine of Cleves (1417–1479)
Catherine of Cleves (25 May 1417 – 10 February 1479) was Duchess of Guelders by marriage to Arnold, Duke of Guelders.
She acted as regent of Guelders during the absence of her spouse in 1450.
The Hours of Catherine of Cleves was commissioned for her.
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.
Reginald II, Duke of Guelders
Reginald II of Guelders, called" the Black"( c. 1295 – 12 October 1343), was Count of Guelders, and from 1339 onwards Duke of Guelders, and Zutphen, in the Low Countries, from 1326 to 1343.
He was the son of Reginald I of Guelders and Marguerite of Flanders.

Question: Who is the paternal grandfather of Reginald I Of Guelders?
Answer: Gerard III, Count of Guelders