Marie de Medici, regent of France, commissioned him in 1614 to negotiate with some members of the États généraux, "whose minds were unwell", and his clever response obtained from them the nomination of a president acceptable to the court.
Until the death of his father, his principal occupation "was to accompany the King and gain the honor of his good graces, to which he succeeds."
The kindness of the queen mother of Louis XI to him was also the affection of the princess to Madame de Brienne, his wife, whom the whole court knew to be the closest confidante of Anne of Austria.
The impairment of the Count of Brienne was not soon enough for the young and voluntary authority of Louis XIV; high diplomatic capacities should preferably also attract the attention of the king, a great kingdom was coming, and he had to carry and moderate both the ideas of the gigantic new prince, physical strength and moral well above that of the Count de Brienne.
By a contract of 7 February 1623,[1] he married Louise de Béon [fr] (1602–1665), who brought him the title of Count of Brienne.