Although de Harlay belonged to the Protestant branch of the family of Harlay, he adopted the Catholic religion in 1572 during the massacres of the Huguenots.
The title, referring to Beaumont-du-Gâtinais in the Île-de-France, was created for Monseigneur Charles-François-Christian de Montmorency-Luxembourg, son of Christian-Louis, prince de Tingry (third son of François-Henri de Montmorency, duc de Luxembourg) and his wife Louise-Madeleine de Harlay, comtesse de Beaumont.
Pope Innocent XI, having made him cardinal instead of Harlay, presented by the king, he was not allowed till 1689 to go to Rome to receive the insignia of his dignity.