Maurice, Prince of Orange
Maurice of Orange (14 November 1567 – 23 April 1625) was "stadtholder" of all the provinces of the Dutch Republic except for Friesland from 1585 at earliest until his death in 1625.
Before he became Prince of Orange upon the death of his eldest half-brother Philip William in 1618, he was known as Maurice of Nassau.
Maurice spent his youth in Dillenburg in Nassau, and studied in Heidelberg and Leiden.
He succeeded his father William the Silent as stadtholder of Holland and Zeeland in 1585, and became stadtholder of Utrecht, Guelders and Overijssel in 1590, and of Groningen in 1620.
As Captain-General and Admiral of the Union, Maurice organised the Dutch rebellion against Spain into a coherent, successful revolt and won fame as a military strategist.
Under his leadership and in cooperation with the Land's Advocate of Holland Johan van Oldenbarnevelt, the Dutch States Army achieved many victories and drove the Spaniards out of the north and east of the Republic.
Maurice set out to revive and revise the classical doctrines of Vegetius and pioneered the new European forms of armament and drill.
During the Twelve Years' Truce, a religious dispute broke out in the Republic, and a conflict erupted between Maurice and Van Oldenbarnevelt, which ended with the latter's decapitation.
After the Truce, Maurice failed to achieve more military victories.
He died without legitimate children in The Hague in 1625, and was succeeded by his younger half-brother Frederick Henry.
Otto I, Count of Nassau
Otto I of Nassau,( † between 3 May 1289 and 19 March 1290) was Count of Nassau and is the ancestor of the Ottonian branch of the House of Nassau.
Elisabeth of Nassau-Dillenburg, Countess of Wied
Elisabeth of Nassau-Dillenburg (1 December 1488 – 3 June 1559 in Dillenburg) was a member of the House of Nassau.
She was a daughter of John V of Nassau-Dillenburg and his wife Elisabeth of Hesse-Marburg.
Her brothers were Henry III of Nassau-Breda, John of Nassau-Vianden-Dietz, Ernest of Nassau and William the Rich.
Her sister was Maria of Nassau.
Henry I, Count of Nassau-Siegen
Henry I of Nassau- Siegen,( – between 13 July and 14 August 1343) was Count of Nassau- Siegen, a part of the County of Nassau, and ancestor of the House of Nassau- Siegen.
He comes from the Ottonian branch of the House of Nassau.
Adolf of Nassau (1540–1568)
Adolf of Nassau (Dillenburg, 11 July 1540 – Heiligerlee, 23 May 1568) was a count of Nassau, also known as Adolphus of Nassau.
He was the fourth son and sixth child of William I, Count of Nassau-Dillenburg and Juliana of Stolberg.
He was the second youngest brother of William the Silent.
Walram II, Count of Nassau
Walram II of Nassau,( – 24 January 1276), was Count of Nassau and is the ancestor of the Walramian branch of the House of Nassau.
Johann VI, Count of Nassau-Dillenburg
Count John VI of Nassau-Dillenburg (22 November 1536 – 8 October 1606) was the second son of William the Rich and the younger brother of William the Silent.
He has a special place in the history of the Netherlands because he is the male-line forefather of the House of Orange which ruled that country until 1898.
John VI of Nassau-Dillenburg was a Count of Nassau in Dillenburg.
Other names he had were "Jan VI" or "Jan de OudeJohn the Elder", to distinguish him from his 2nd son, "John the Middle", and his grandson "John the Younger").
John VI was born in Dillenburg, the second son of Count William I of Nassau-Dillenburg and his second wife Juliane of Stolberg-Wernigerode and brother of William I of Orange.
He was the principal author of the Union of Utrecht.
William I, Count of Nassau-Dillenburg
William I, Count of Nassau- Dillenburg( nicknamed" William the Rich",; 10 April
1487 – 6 October 1559) was a count of Nassau- Dillenburg from the House of Nassau.
His nickname" the Rich" refers to him having many children.
However, he owned a number of counties: Nassau- Dillenburg, Nassau- Siegen, Nassau- Dietz and Vianden.
William was born in Dillenburg as the younger son of Count John V of Nassau- Dillenburg and Landgravine Elisabeth, daughter of Landgrave Henry III of Hesse- Marburg and Anna of Katzenelnbogen.
He was the brother of count Henry III of Nassau- Breda and the father of William I of Orange.
His eldest son William the Silent inherited the principality of Orange in Southern France from his cousin René of Chalon, as well as the vast properties of the House of Nassau- Dillenburg in the Netherlands from his father, which Engelbert I of Nassau had received by marriage in 1403.
The early House of Orange- Nassau descends from William I., the Silent, while the later House of Orange- Nassau( and the Dutch royal family) descends in the male line from his younger brother John, Count of Nassau- Dillenburg, and from the latter's fifth son, Count Ernst Casimir of Nassau- Dietz, however in the female line also from William of Orange.
William of Nassau (1601–1627)
Willem van Nassau, Lord of De Lek (also "Willem van Nassau-LaLecq", or in French
"Willem LaLecq"; 18 August 1601 – 18 August 1627) was a Dutch soldier from 1620 until 1627.
He was the illegitimate son of stadholder Maurice of Nassau, Prince of Orange and his mistress Margaretha van Mechelen.
Like their other illegitimate children, he was recognized with the surname Nassau-LaLecq.
He went by the title Rijksgraaf (Count of the Holy Roman Empire)
van Nassau-LaLecq" and was also popularly known in French as the "Chevalier de Nassau".
After 1625 he was granted lands and the title Lord of De Lek.
He received his heerlijkheid of De Lek as a bequest from his father to him and his descendants.
His brother Lodewijk van Nassau had the title "Lord of Beverweerd and Odijk".
From his 19th year on, Willem served in the Dutch army fighting Spain in the Dutch Revolt (1568–1648).
Aged only 24 he received the rank of lieutenant-admiral of Holland and West Friesland, replacing stadholder Frederik Hendrik.
He led the Dutch ships that participated in the Cádiz expedition of 1625.
In the summer of 1627 he was present at the Siege of Grol.
On the 18 August, not long before the end of the siege, fighting with the French troops at the front, Willem received a bullet wound which later proved fatal.
Thus he died on his 27th birthday, with Lodewijk inheriting Willem's fiefdom.
On 4 April 1627, 4 months before his death, Willem married Anna van der Noot, lady of Hoogwoud and Aartswoud, in Sluis.
Though he had no children with Anna, he had one illegitimate son by Barbara Augustinus Cocx, Willem Jonker van Nassau (1620-1679) .
Frederick Augustus, Duke of Nassau
Friedrich August, Duke of Nassau, Prince of Nassau- Usingen( 23 April 1738 in Usingen – 24 March 1816 in Wiesbaden) was the last Prince of Nassau- Usingen and, jointly with his cousin, Friedrich Wilhelm of Nassau- Weilburg, first Duke of Nassau.
He died without surviving male issue and was succeeded by his cousin's son, Wilhelm.

Question: Who is the paternal grandfather of William Of Nassau (1601–1627)?