John Francis Desideratus was the only son of Count John VIII of Nassau-Siegen, who had converted to Catholicism, and Ernestine Yolande de Ligne d'Amblise. He succeeded his father in 1638 as count of Nassau-Siegen, but had to cede a part of the County to the Protestant branch of the family in 1648. He kept fighting his Protestant neighbours and suppressing the Calvinists in his territory. His reign was marked by bad management and debts. Like his father, John Francis Desideratus was a general in Spanish service. In 1652, he was elevated to Imperial Prince and became a Lord in the Order of the Golden Fleece. In 1661, he was promoted to Knight in the Order of the Golden Fleece. From 1665 to 1684, he was Spanish stadtholder of Limburg and from 1680 to 1699 also of Upper Guelders. He lived a large part of his life in Roermond, where he died in 1699. At his death he was succeeded by his eldest surviving son William Hyacinth.
Marriages and children
John Francis Desideratus married 3 times: In Vienna on 14 May 1651 he married Countess Johanna Claudia of Königsegg-Rotenfels-Aulendorf, Lady-in-waiting of Empress Eleonora Gonzaga during 1648–1651. They had ten children:
Clara Juliana Margarethe Felicitas, Canoness of the High Noble Imperial Abbey at Thorn and of the St. Waadru Convent at Mons.
Albertina Anna Gabriella, Canoness of the Noble Abbey of St. Aldegonde at Maubeuge.
Maria Donata Gabriella.
Louise Carolina Anna.
A daughter.
Stillborn son.
In Rodemachern 31 May 1665 he married Margravine Marie Eleonore Sophie of Baden-Baden in Rodemachern. They had four children:
Francis Fortunatus.
William Hyacinth, Prince of Nassau-Siegen, twin with Hermann.
Hermann, twin with William Hyacinth.
Maria Eleonora Ernestina.
In Brussels on 9 February 1669 he married Baroness Isabella Clara du Puget de la Serre. They had ten children:
Alexius Andreas Anton Ferdinand Christian, Canon at Cologne,, Dean of the St. Peter Church and Chancellor of the University at Louvain, Deacon at Cologne, Priest, Canon at Liège, Abbot of the St. Croix de Bouzonville Monastery, Titular Archbishop of Trapezopolis, Knight of the Order of Malta.
Joseph.
Charlotte Sophia Johanna.
Joseph Maurice Karl.
Maria Philippina.
Francis Hugo Ferdinand Gereon, Vice-Regent of Nassau-Siegen ; married to Countess Leopoldine of Hohenlohe-Bartenstein, without issue.
Anna Louise Francisca, married to Charles Damman, Viscount d'Oomberghe.
Clara Bernardina Francisca, married to Francisco de Sousa Pacheco.
Emmanuel Ignatius, Baron de Renaix, Prince-Regent of Nassau-Siegen,, Fieldmarshal of the Spanish Army, Knight of the Order of Malta, Knight of the Order of the Golden Fleece, Knight of the Order of St. Hubertus ; married in 1711 to Charlotte de Mailly-Nesle; they became formally separated in 1716 without surviving issue. He was the probable grandfather of Charles Henry of Nassau-Siegen.
Jeanne Baptista Josefina, Canoness of the St. Waadru Convent at Mons.
