Count John of Nassau-Idstein (born 24 November 1603 in Saarbrücken; died: 23 May 1677 in Idstein) was Count of Nassau and Protestant Regent of Idstein. Life His parents were Louis II, Count of Nassau-Weilburg (1565–1627) and his wife, Landgräfin Anna Maria of Hesse-Kassel (1567–1626). His father had in 1605 reunited all the possessions of the Walram line of the House of Nassau: Saarbrücken, Weilburg and Idstein. His brother was William Louis. When the brothers divided their father's inheritance on 29 January 1629 in Ottweiler, William Louis received the County of Saarbrücken, the district of Ottweiler, the Bailiwick of Herbitzheim, and the community of Saarwellingen. John received the Lordship of Idstein, Wiesbaden and Sonnenberg. The two younger brothers, Ernest Casimir and Otto received Wehener Grund and the district of Burgschwalbach. However, since they were still minors, William Louis administered those territories as regent. Shortly thereafter, their territories were put at risk by the Imperial Edict of Restitution of 2 March 1629, when the Prince-Archbishops of Mainz and Trier claimed restitution of church properties that had been confiscated after the Peace of Passau of 1552. On 7 July 1629, the Reichskammergericht ruled that the House of Nassau had to return city and castle of Sarrewerden, Bouquenom and Wieberstweiler to the Bishopric of Metz as fiefs of Lorraine. They were allowed to keep their other disputed possessions. In 1629 he married Sibylla Magdalena of Baden-Durlach (born: 21 July 1605; died: 26 July 1644 in Strasbourg), daughter of George Frederick, Margrave of Baden-Durlach and Wild- and Rhinegravine Juliane Ursula of Salm-Neufville. When, at the end of that year, King Gustavus Adolphus of Sweden appeared the Rhine, presented William Louis, John and Ernest Casimir joined him in his war against the Emperor. After King Gustavus Adolphus had fallen on 16 November 1632, the three counts committed themselves on a meeting of Protestant princes in Heilbronn to continue fighting the Emperor, now under the Swedish Chancellor Axel Oxenstierna. John signed the alliance with France against the Emperor on 5 September 1633, as the representative of the Nassau brothers. The youngest brother, Otto, died on 24 November 1632. On 11 December, Ernest Casimir came of age and the brothers decided to revise the division of the inheritance. In this new division, Ernest Casimir received the districts of Weilburg and Mehrenberg, the County of Gleiberg and the districts of Kirchheim and Stauf, which had been Otto's. The brothers