Joanna of Hainaut
Joanna of Hainault( 1315–1374) was a Duchess of Jülich by marriage to William V, Duke of Jülich.
She was the third daughter of William I, Count of Hainaut, and Joanna of Valois.
She was a younger sister of Philippa of Hainault, Queen of England, and Margaret II of Hainault.
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:
William V, Duke of Jülich
William V, Duke of Jülich( – 25/26 February 1361) was a German nobleman.
Some authors call him William I, because he was the first" Duke of Jülich"; the earlier Williams had been" Count of Jülich".
Other authors call the subject of this article" William VI"; they count the son and co-ruler of William IV as William V. William V was the eldest son of Gerhard V of Jülich and Elisabeth of Brabant- Aarschot, daughter of Godfrey of Brabant.
William V was a key political figure of his time, being a brother- in- law to both Edward III of England and Emperor Ludwig IV.
He spent enormous sums of money to have his brother Walram of Jülich appointed as Archbishop of Cologne over Adolph II of the Marck.
In 1337 he was crucially involved in the German- English alliance which caused the start of the Hundred Years' War. William was an important supporter of Emperor Ludwig and for a time, he supported the Habsburgs against the House of Luxembourg in the Carinthian war of succession.
Upon the collapse of the German- English alliance and the death of his brother- in- law, William switched his allegiance to Emperor Charles IV.
In 1352 he initiated an inheritance tax on Heinsberg- Valkenburg/ Monschau.
William won important positions through his Archbishop brother and also served for a time as a field captain for Flanders in the Hundred Years' War.
His sons fought against him during an uprising of part of the Jülich knighthood which opposed inclusion in the increasing territorial state, and he was imprisoned by them in 1349, but released in 1351 due to public pressure.
Upon his father's death in 1328, William became Count of Jülich.
In 1336 William was appointed Margrave by his brother- in- law, Emperor Ludwig IV, and in 1356/ 57 he was raised to the level of Duke by Emperor Charles IV, thus becoming the first Duke of Jülich.
His skillful marriage policy, especially the marriage of his son Gerhard to Margaret of Ravensberg, heiress of Berg and Ravensberg, enabled him to add territory to the house of Jülich.
Upon William's death in 1361, the Duchy of Jülich passed to his second son, William, his eldest son having predeceased.
William and his wife are buried in Nideggen.
He seems to have held the title of Earl of Cambridge from 1340 to his death.
Reforce d'Agoult
Reforce d' Agoult was the Angevin seneschal of medieval Lombardy, under the reign of Joanna I of Naples.
Killed in battle at Gamenario, he was replaced by Roberto di Luinardo.
William IV, Duke of Jülich-Berg
William IV of Jülich- Berg( 9 January 1455 – 6 September 1511) was the last ruler of the Duchy of Jülich- Berg.
Otto, Duke of Brunswick-Grubenhagen
Otto, Duke of Brunswick- Grubenhagen( 1320 – 1 December 1398) was the fourth and last husband of Joanna I of Naples.
He also held the title of Prince of Taranto.
His nickname was Otto the Tarantine.
Joanna of Jülich
Joanna of Jülich (died 1394) was the youngest daughter of Duke William II and his wife, Marie of Guelders.
Adolf, Duke of Jülich-Berg
Adolf, Duke of Jülich- Berg( c. 1370 – 14 July 1437), was the first Duke of the combined duchies of Jülich and Berg.
He was the son of William VII of Jülich, 1st Duke of Berg and Anna of the Palatinate.
In 1397, Adolf rebelled against his father along with his brother William, ravaged Düsseldorf and imprisoned his father.
He was outlawed and was subsequently subdued in 1405.
Upon his father's death in 1408, Adolf became the 2nd Duke of Berg.
Adolf fought against Lorraine and other pretenders for Bar but surrendered after his capture in 1417.
His father's cousin, Reginald, Duke of Jülich and Guelders, had no heirs and upon his death in 1423, Adolf succeeded him in three- fourths of the Duchy, the fourth quarter( called" Jülicher Quart") was inherited by John II of Loon, Lord of Heinsberg and Löwenberg, grandson of the first duke of Jülich, William V.
The dukedom of Jülich passed to Adolf, thus becoming the first duke of the combined duchies of Jülich and Berg. John II. of Loon- Heinsberg was than also called Lord of Jülich.
Adolf also began a year- long hereditary war against the House of Egmond for the dukedom of Guelders but could not win even with financial support from Sigismund, Holy Roman Emperor, who supported Adolf in this fight despite Adolf's opposition to Sigismund's coronation at Aachen in 1414.
Adolf supported the Roman candidate in the Council of Constance which ended the Western Schism.
He traditionally fought against the Archbishop of Cologne.
He later secured Monschau- Montjoie and in 1428 he seized Lievandal- Wevelinghoven.
Adolf had only one son who died before him so after Adolf's death in 1437, the dukedom of Jülich- Berg passed to his nephew Gerhard, son of his brother William.
Adolf died in Cologne on 14 July 1437 and is buried at Great St. Martin Church, Cologne.
Andrew, Duke of Calabria
Andrew, Duke of Calabria( 30 October 1327 – 18 September 1345) was the first husband of Joanna I of Naples, and a son of Charles I of Hungary and brother of Louis I of Hungary.
William II, Duke of Jülich
William II, Duke of Jülich( – 13 December 1393) was the second Duke of Jülich and the sixth William in the House of Jülich.
He was the second son of William I of Jülich and Joanna of Hainaut.
William was co-ruler from 1343.
He quarreled greatly with his father and imprisoned him from 1349- 1351.
He tried for many years in Holland- Zeeland to enforce claims against the House of Wittelsbach but failed.
When his father died in 1361, William became the second Duke of Jülich, his elder brother Gerhard having predeceased their father.
He led the traditional feuds of the House of Jülich and lost Kaiserswerth and Zülpich, among others.
William intervened in favor of Edward in the catastrophic war of succession between his brothers- in- law Reinald and Edward for control of the Duchy of Guelders.
He took part in the 1371 Battle of Baesweiler( in which Edward was mortally wounded) and captured Wenceslaus I, Duke of Luxembourg.
His brother- in- law Reinald died later in 1371 and as neither Reinald nor Edward left heirs, another fight for the succession of Guelders arose between William and his wife Maria( sister to Reinald and Edward) and Maria's sister Mathilde, wife of John II, Count of Blois.
In 1377, Emperor Charles IV granted Guelders to William's son William, but the title was not secured until 1379.
Among other territories, William acquired Monschau- Montjoie, Randerath and Linnich.

Question: Who is the maternal grandfather of Joanna Of Jülich?
Answer: Reginald II, Duke of Guelders