A scion of the famous French Montesquiou family, he was the fourth son of Henri I de Montesquiou, seigneur d'Artagnan by his wife Jeanne, daughter of Jean de Gassion. He was also the cousin of Charles de Batz de Castelmore, to whom he lent one of his titles, comte d'Artagnan, on whom the hero of Alexandre Dumas, père's D'Artagnan Romances was based.
A descendant of the prominent French Montesquiou family, he was the fourth son of Henri I de Montesquiou, seigneur d'Artagnan, by his wife Jeanne, daughter of Jean de Gassion. He was also related to Charles de Batz de Castelmore, who received one of his titles, comte d'Artagnan, from him, which inspired the hero of Alexandre Dumas, père's D'Artagnan Romances.