Jane Marcet was born Jane Haldimand in London on 1 January 1769, one of twelve children of wealthy merchant and banker Anthony Francis Haldimand (1740/41–1817) and his wife Jane (died 1785). Following Swiss tradition, she was educated at home with her brothers: her studies included Latin (essential for the sciences), chemistry, biology, and history, as well as topics more usual for young ladies in England. Jane took over the running of the family at age 15, after her mother's death. She managed the house and helped to bring up her younger siblings. Her younger brother William Haldimand (1784–1862) became a director of the Bank of England and a member of Parliament. She also acted as her father's hostess, helping to entertain frequent parties of scientific and literary guests. Jane developed an early interest in painting during a visit to Italy with her father in 1796, and studied with Joshua Reynolds and Thomas Lawrence. Her artistic training later enabled her to illustrate her books.