Born at Langenschwalbach, he was the eldest child of Ernest Leopold, Landgrave of Hesse-Rotenburg and his wife Eleonore of Löwenstein-Wertheim-Rochefort.
He was Heir apparent to the Landgraviate of Hesse-Rotenburg from his birth, and held the title till his death.
His siblings included Polyxena, future Queen of Sardinia; Caroline, future Princess of Condé and wife of Louis Henri, Duke of Bourbon, Prime Minister of France.
In 1753, his wife married again Nicolaus Leopold, Prince of Salm-Salm (1701-1770), but had no children.
[1] The couple were married at Anholt and later produced four children, two of which would die young and one who would go on to have progeny: