He was the only son of the "fermier général" Pierre Grimaud du Fort. In 1766, 18 years after his father's death, he reached his majority and assumed control of his enormous inheritance from his father, making him one of the richest men of his day. Work on the gardens of the family chateau at Orsay, begun by his father and continued by Pierre Gaspard's guardians, including, in 1758, extensive work under the direction of the talented architect Jean-Michel Chevotet, who had won the Prix de Rome in 1722 and was admitted to the Royal Academy of Architecture in Paris in 1732. When the ambitious garden scheme was completed on 1 August 1764, two years before his majority, an inventory of the d'Orsay family holdings declared: He acquired in 1768 the hotel de Saissac, 69 rue de Varenne, Paris. This had been built for Jeanne Therese Pelagie d'Albert de Luynes, marquise de Saissac, in 1708, and Pierre had it rebuilt by Pierre Convers, Jean Augustin Renard et Charles Joaquim Benard, with the old bedroom made into a salon, for example. This phase of the hotel – of which nothing remains today – constituted an important step in the evolution of the taste, and contributed to his entry into aristocratic circles of the Faubourg Saint-Germain. He married Marie Louise Amélie de Croÿ, princesse de Croÿ-Molembais, daughter of Prince Guillaume François de Croÿ et Princess Anne Françoise Amélie de Trazegnies, on 31 December 1770. Earlier in 1770 Pierre Gaspard had been raised to the title of comte by Louis XV. Marie-Louise and Pierre had one child, Albert-Jean-François-Louis-Marie Grimaud. Marie Louise died giving birth to him, and Pierre began travelling Europe for consolation, gathering famous collections of paintings and sculptures. On his travels he also found a new wife, Marie Anne de Hohenlohe-Waldenburg-Bartenstein, of the :de:Haus Hohenlohe|house of Hohenlohe-Waldenburg-Battenstein, whom he married on 22 August 1784. The couple moved to Germany in 1787, meaning that – on the outbreak of the French Revolution two years later – Gaspard's property in France was seized, he was declared an Émigré, and they were left in the poverty in which he died.
