In 1786 he married Albertina Marianna Gaulis (d. 1798), daughter of Jean Abraham Rodolph Gaulis (d. 1788) of
Lausanne, Switzerland, an important magistrate of that city. He is described as "notaire juré, conseiller, secrétaire baillival, banneret de la Cité". In 1779 he resigned as "secrétaire baillival" after 40 years' service and requested that his son J. Juste Gaulis should succeed him, who had seconded for him during the last three years of his term. The request was successful as the son was appointed to the position in 1780. Her mother was Jeanne-Louise-Dorothée Porta, from another prominent Lausanne family. Her eldest brother was Abram Frederic Louis Juste Gaulis, a member of the
Grand Council of Vaud and the heir and custodian of the Château de
Colombier-sur-Morges, near Lausanne. Another brother was Charles Gaulis (died in Germany 23 August 1796), who fathered a child by
Mary Jane de Vial (later Clairmont). Charles Gaulis Clairmont, who grew up as stepbrother to
Mary Shelley, ended up as Chair of English literature at
Vienna University Among the children of Albertina and Robert Trefusis were: • Robert Cotton St John Trefusis, 18th Baron Clinton (28 April 1787 – 1 October 1832), married Marie Charlotte Mederacke. • Hon Marianne Conventry Trefusis (31 May 1789 – 3 March 1806) • Hon Anne Matilda Tefusis (28 June 1790 – 24 February 1876), married Edward George Moore, and was the mother of the
6th Earl Mount Cashell (1829–1915) •
Charles Rodolph Trefusis, 19th Baron Clinton (9 November 1791 – 10 April 1866) • Captain George Rolle Walpole Trefusis RN (8 April 1793 – 1 March 1849) • Hon Louisa Barbara Trefusis (29 December 1795 – 20 November 1885), Lady Rolle after her marriage to Sir John Rolle. ==Sources==