In 1744 Louis XV negotiated a marriage between his fifteen year old son and the nineteen year old Infanta Maria Teresa Rafaela of Spain , daughter of King Philip V of Spain and Elisabeth Farnese . In 1744 Louis XV negotiated a marriage between his fifteen-year-old son and the nineteen-year-old Infanta Maria Teresa Rafaela of Spain , daughter of King Philip V of Spain and his Italian wife , Elisabeth Farnese , and first cousin , once removed , of Louis XV .