Francis Alexander was the son of prince Maurice Henry of Nassau-Hadamar (23 April 1626 – 24 January 1679) and his second wife Maria Leopoldine of Nassau-Siegen (1652–1675).

He died as a result of a fall from his horse near the Limburg Gate (now called the Hammelburg) in Hadamar on 27 May 1711.

He was buried in the princely crypt in the Franciscan church at the Mönchsberg in Hadamar, wearing the robe of a Reichskammergericht judge.

On 18 October 1695 in Lovosice (Bohemia), Francis Alexander married Elizabeth Catherine Felicitas (14 February 1677 Rheinfels Castle near St. Goar – 15 May 1739 in Dietz, buried in the Franciscan monastery St. Martin at Boppard), the daughter of William "the Elder" of Hesse-Rheinfels-Rotenburg.

Even after Ernestine had entered the convent at Altenberg, near Wetzlar, and despite mediations efforts by Archbishop John VIII of Trier and Emperor Joseph I, Francis Alexander and his wife could not reconcile their differences.

Francis Alexander is shown wearing a metal armour and beside him is a gleaming crown, decorated with pearls and a golden cross.