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 member of the renowned 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 a 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.