 Gabriel de Rochechouart de Mortemart was the son of Gaspard de Rochechouart de Mortemart, Marquis of Mortemart, and of Louise de Maure, "suo jure" Countess of Maure.His younger brother, Louis de Rochechouart de Mortemart, died without children in 1669.He spent a great part of his childhood with the future king of France Louis XIII, until the assassination of the latter's father, Henry IV, in 1610.