Franz Stephan married Maria Theresa in 1736, thus founding the House of Habsburg-Lorraine. In 1740, following the sudden death of Charles VI, he became co-regent of the Habsburg patrimonial lands. The title of Holy Roman Emperor passed to a Wittelsbach who died in1745, leaving Franz Stephan to be elected emperor as Franz I. Thanks to his financial expertise he left a huge personal fortune that was used to establish the Familienversorgungsfonds (‘family support fund’), which existed until 1919.