From Wikipedia

The Medici

Part Three

The Medici Popes

 The Medici remained masters of Italy through their two famous 16th century popes, Leo X and Clement VII, who were de facto rulers of both Rome and Florence. They were both patrons of the arts, but in the religious field they proved unable to stem the advance of Martin Luther's ideas. Another Medici became Pope: Alessandro Ottaviano de' Medici (Leo XI).

The most outstanding figure of the 16th century Medici was Cosimo I, who, coming from relatively modest beginnings in the Mugello, rose to supremacy in the whole of Tuscany, conquering the Florentines' most hated rival Siena and founding the Grand Duchy of Tuscany. Cosimo purchased a portion of the island of Elba from the Republic of Genoa and based the Tuscan navy there. He died in 1574, succeeded by his elder surviving son Francesco. His inability to produce male heirs led to the succession of his younger brother, Ferdinando, upon his death in 1587. Francesco married Johanna of Austria, and had Eleonora de' Medici, Duchess of Mantua, and Marie de' Medici, Queen of France and of Navarre. Through the latter, every succeeding French monarch (bar the Napoleons) are descended from Francesco.