Sibylla of Burgundy, Duchess of Burgundy
Sybilla of Burgundy( 1065 – 1103), was a French noble, Duchess consort of Burgundy by marriage to Eudes I, Duke of Burgundy.
She was a daughter of William I, Count of Burgundy and Stephanie.
She was married to Eudes I, Duke of Burgundy in 1080.
Children:
Florine of Burgundy
Florine of Burgundy( 1083–1097) was a French crusader.
She was the daughter of Eudes I, Duke of Burgundy and Sybilla of Burgundy.
Her maternal grandfather was William I, Count of Burgundy.
Florine was married to Sweyn the Crusader, a son of Sweyn II of Denmark.
Humbert II, Count of Savoy
Umberto II, nicknamed the Fat( 1065, Carignano, Piedmont – 19 October 1103), was Count of Savoy from 1080 until his death in 1103.
He was the son of Amadeus II of Savoy.
He was married to Gisela of Burgundy, daughter of William I, Count of Burgundy, and had 7 children:
Robert, Count of Burgundy
Robert, Count of Burgundy( 1300 – 1315) was the son of Otto IV, Count of Burgundy and Mahaut, Countess of Artois.
He was count of Burgundy between 1302 and 1315.
He died in 1315, and was succeeded by his sister, Joan II, and brother- in- law, Philip II, later queen and king of France.
Isabella of Bourbon
Isabella of Bourbon, Countess of Charolais( 1434 – 25 September 1465) was the second wife of Charles the Bold, Count of Charolais and future Duke of Burgundy.
She was a daughter of Charles I, Duke of Bourbon and Agnes of Burgundy, and the mother of Mary of Burgundy, heiress of Burgundy.
Reginald I, Count of Burgundy
Reginald I, Count of Burgundy( aka Renaud I, Count Palatine of Burgundy) was the second Count of the Free County of Burgundy.
Born in 986, he was the son of Otto- William, Count of Burgundy( the first Count) and Ermentrude de Roucy.
In 1016, Reginald married Alice of Normandy.
He succeeded to the County on his father's death in 1026.
Reginald was succeeded by his son, William I, on his death in 1057.
Reginald married Alice and had the following children:
William I, Count of Burgundy
William I (1020 – 12 November 1087), called the Great ("le Grand" or "Tête Hardiethe Stubborn"), was Count of Burgundy from 1057 to 1087 and Mâcon from 1078 to 1087.
He was a son of Renaud I and Alice of Normandy, daughter of Richard II, Duke of Normandy.
William was the father of several notable children, including Pope Callixtus II.
In 1057, he succeeded his father and reigned over a territory larger than that of the Franche-Comté itself.
In 1087, he died in Besançon, Prince-Archbishopric of Besançon, Holy Roman Empire -- an independent city within the County of Burgundy.
He was buried in Besançon's Cathedral of St John.
William married a woman named (a.k.a. Etiennette).
Children of Stephanie (order uncertain):
Héctor Barrantes
Héctor Barrantes Sansoni( 1939–1990) was an Argentine polo player.
He was the stepfather of Sarah, Duchess of York.
Alice of Normandy
Alice or Adeliza, Adelaide or Aelis
(c. 1002 – 1038) was a countess consort of Burgundy, the daughter of Richard II, Duke of Normandy (972–1026) and Judith of Brittany.
She married Reginald I, Count of Burgundy and had the following children:
Jerrold Wexler
Jerrold Wexler( June 27, 1924 – November 10, 1992) was a noted American businessman and film producer.
He was the brother of cinematographer Haskell Wexler and the stepfather of actress Daryl Hannah.

Question: Who is William I, Count Of Burgundy's father?
Answer: Reginald I, Count of Burgundy