His mother was a daughter of Gabriel Michel de Tharon [fr], who was involved in the Nantes slave trade and director of the French East India Company 1749–1764.
At the age of 16, he was promoted to captain of the bodyguard of Monsieur, the Count of Provence, brother of the king, the future Louis XVIII.
With Louis Doulcet de Pontécoulant, a fellow student at the Artillery School, he then went on a long six-month mission to Prussia (July 1784-January 1785).
This pre-eminent position facilitated his election in March 1789 to the only seat reserved for the nobility to represent the Bailiwick of Senlis at the Estates-General.
He emigrated after 10 August 1792, joined the army of the Princes, where he was poorly received, and eventually served as a private in an Austrian regiment.
During the revolutionary decade, the Duke and Duchess de Lévis travelled back and forth between France and England several times, either together or separately.
At the age of 20, Gaston de Lévis married Pauline Charpentier d'Ennery on 13 May 1784 at the church of Saint-Eustache in Paris.
Aged 13, she was the only daughter of Victor-Thérèse Charpentier, count then marquis of Ennery, marshal of the King's camps and armies, governor of Martinique and then Saint Domingue, who died in 1776, and Rose Bénédicte d'Alesso d'Éragny.
Gaston and his wife made the Château d'Ennery [archive] their favourite residence, carrying out numerous improvements and embellishments.
The quotation often attributed to Voltaire, "Judge a man by his questions rather than by his answers" is a version of one maxim by Lévis: "Il est encore plus facile de juger de l'esprit d'un homme par ses questions que par ses réponses."