The passion of Henri IV for this lady was so great that he declared his intention of obtaining a divorce from Marguerite de Valois, for the purpose of making her his wife; a project from which he was dissuaded by D'Aubigny, who represented that the contempt which could not fail to be felt by the French for a monarch who had degraded himself by an alliance with his mistress, would inevitably deprive him of the throne in the event of the death of Henri III and the Duc d'Alencon.
[29] Gabrielle d'Estrees was the daughter of Antoine d'Estrees, fourth of the name, Governor, Seneschal, and first Baron of Boulonnois, Vicomte de Soissons and Bersy, Marquis de Coeuvres, Knight of the Orders of the King, Governor of La Fere, Paris, and the Isle of France; and of Francoise Babou, second daughter of Jean, Seigneur de la Bourdaisiere, and of Francoise Robertet.

She married at an early age, by the desire of her father, who was anxious to protect her from the assiduities of the King, Nicolas d'Armeval, Seigneur de Liancourt, who was, alike in birth, in person, and in fortune, unworthy of her hand.

This ill-assorted union produced the very result which it was intended to avert, for Henry found means to separate the young couple immediately after their marriage, and to attach Gabrielle to the Court, where she soon became the declared favourite.

On the birth of her first child (Cesar, Duc de Vendome), Madame de Liancourt abandoned the name of her husband, from whom she obtained a divorce, and assumed that of Marquise de Monceaux, which she derived from an estate presented to her on that occasion by the King; and on the legitimation of her son in January 1595, she already aspired to the throne, and formed a party, headed by M.de Sillery, by whom her pretensions were encouraged.

She was subsequently created Duchesse de Beaufort, and became the mother of Catherine-Henriette, married to the Duc d'Elboeuf, and of Alexandre de Vendome, Grand Prior of France, who were likewise legitimated.