The origins of de Lesseps' family are traceable back as far as the end of the 14th century. His ancestors, it is believed, came from Spain, and settled at Bayonne during the region's occupation by the English. One of his great-grandfathers, Pierre de Lesseps (Bayonne, 2 January 1690 – Bayonne, 20 August 1759), son of Bertrand Lesseps (1649–1708) and wife (m. 18 April 1675) Louise Fisson (1654–1690), was town clerk and at the same time secretary to Queen Anne of Neuberg, widow of Charles II of Spain, exiled to Bayonne after the accession of Philip V, and married on 7 January 1715 his great-grandmother Catherine Fourcade (2 June 1690 – 22 August 1760), by whom he had fourteen children, six of whom died in childhood: Dominique de Lesseps (1715–1794), Pierre de Lesseps (1716 – ?), Marie de Lesseps (1717–1722), Arnaud de Lesseps (1719–1726), Jean-Barthélémy de Lesseps (1720–1795), Marcel de Lesseps (1720–1730), Jean-Pierre de Lesseps (1721–1721), Catherine de Lesseps, Gracy de Lesseps (1725–1791), Plaisance de Lesseps (1727–1735), Michel de Lesseps (1729–1801), married in 1769 to Florence Verdier (1739–1822) (parents of Louise Thérèse de Lesseps (1770–1866), married in 1788 to Mathieu Belland (1764–1817), Martin de Lesseps (1730–1807), married to Anna Caysergues (1730–1823) and had issue, Jeanne de Lesseps (1733 – ?), married in 1759 to Alex Andre Dubrocq, and Etiennette de Lesseps (1735 – ?), married in 1761 to Pierre Simonin.