[1] After Charles-Jules died as a child, Louis-Charles-Casimir forfeited his claim to a secular inheritance by joining the Order of the Holy Cross, whereupon Hercule Mériadec became Comte de Rochefort.

[1] His father was the fifth Duc de Montbazon, but succession to that title remained uncertain until François-Armand died without living children at the age of 35 in 1717,[1] leaving Hercule-Mériadec to become Prince de Guéméné, the title usually borne by the heir apparent.

Only when his father died in October 1727 did he succeed to the Montbazon ducal peerage and become head of the House of Rohan,[1] which enjoyed the high rank of princes étrangers at the court of Louis XVI.

While serving in the Gendarmes de la Garde, he held the position of standard-bearer of the company.

His wife presented their daughter, Charlotte Louise, to Louis XV and the queen, Marie Leszczyńska, during the Honneurs de la Cour on 26 October 1737 at Fontainebleau, two days before her marriage.