Francis was born in
Lunéville,
Lorraine (now in France), the fourth and oldest surviving son of
Leopold, Duke of Lorraine, and his wife Princess
Élisabeth Charlotte d'Orléans. He was connected with the
Habsburgs through his grandmother
Eleonore, daughter of Emperor
Ferdinand III. He was very close to his brother
Charles and sister
Anne Charlotte. Emperor
Charles VI favoured the family, who, besides being his cousins, had served the house of
Habsburg with distinction. He had designed to marry his daughter
Maria Theresa to Francis' older brother
Leopold Clement. On Leopold Clement's death, Charles adopted the younger brother as his future son-in-law. Francis was brought up in
Vienna with Maria Theresa with the understanding that they were to be married, and a real affection arose between them. At the age of 15, when he was brought to Vienna, he was established in the
Silesian
Duchy of Teschen, which had been
mediatised and granted to his father by the Emperor in 1722. Francis succeeded his father as
Duke of Lorraine in 1729. In 1731 he was initiated into freemasonry (
Grand Lodge of England) by
John Theophilus Desaguliers at a specially convened lodge in
The Hague at the house of the British Ambassador,
Philip Stanhope, 4th Earl of Chesterfield. During a subsequent visit to England, Francis was made a Master Mason at another specially convened lodge at
Houghton Hall, the
Norfolk estate of British Prime Minister
Robert Walpole. Maria Theresa arranged for Francis to become "
Lord Lieutenant" (locum tenens) of
Hungary in 1732. He was not excited about this position, but Maria Theresa wanted him closer to her. In June 1732 he agreed to go to the Hungarian capital, Pressburg (today's
Bratislava). When the
War of the Polish Succession broke out in 1733,
France used it as an opportunity to seize Lorraine, since France's chief minister,
Cardinal Fleury, was concerned that, as a Habsburg possession, it would bring Austrian power too close to France. A preliminary peace was concluded in October 1735 and ratified in the
Treaty of Vienna in November 1738. Under its terms,
Stanisław I, the father-in-law of King
Louis XV and the losing claimant to the Polish throne, received Lorraine, while Francis, in compensation for his loss, was made heir to the
Grand Duchy of Tuscany, which he would inherit in 1737. In March 1736, the Emperor persuaded Francis, his future son-in-law, to secretly exchange Lorraine for the Grand Duchy of Tuscany. France had demanded that Maria Theresa's fiancé surrender his ancestral Duchy of Lorraine to accommodate the deposed King of Poland. The Emperor considered other possibilities (such as marrying her to the future
Charles III of Spain) before announcing the engagement of the couple. If something were to go wrong, Francis would become governor of the
Austrian Netherlands.
Elisabeth of Parma had also wanted the Grand Duchy of Tuscany for her son
Charles III of Spain;
Gian Gastone de' Medici was childless and was related to Elisabeth via her great-grandmother
Margherita de' Medici. As a result, Elisabeth's sons could claim by right of being a descendant of Margherita. Although fighting stopped after the preliminary peace, the final peace settlement had to wait until the death of Gian Gastone in 1737, to allow the territorial exchanges provided for by the peace settlement to go into effect. On 31 January 1736, Francis agreed to marry Maria Theresa. He hesitated three times (and laid down the feather before signing). Especially his mother
Élisabeth Charlotte d'Orléans and his brother
Prince Charles Alexander of Lorraine were against the loss of Lorraine. On 1 February, Maria Theresa sent Francis a letter: she would withdraw from her future reign, when a male successor for her father appeared. ==Marriage==