[1] Charles was born in Usingen, the son of William Henry of Nassau-Usingen and Countess Charlotte Amalia of Nassau-Dillenburg.

After Charles' father died in 1718, Charlotte Amalia acted as regent for both Charles and his younger brother William Henry II.

In 1728, Charles inherited the counties of Nassau-Ottweiler, Nassau-Idstein and Nassau-Saarbrücken from his second cousin Frederick Louis.

Charles received Usingen, Idstein, Wiesbaden and Lahr; William Henry II received Nassau-Saarbrücken and some smaller territories.

On 26 December 1734 Charles married Princess Christine Wilhelmine of Saxe-Eisenach (born: 1711), a daughter of Duke John William III.