On 14 November 1644 Pope Innocent X created Giancarlo a cardinal-deacon as a token of his affection toward the Medici.[1] Thus forced to give up his military career and with it the title of "General of the Spanish Seas", Giancarlo could not reconcile himself to his new "religious" lifestyle.[2]
Cardinal de' Medici participated in the papal conclave, 1655 as one of leaders of the Spanish faction. Pope Alexander VII made Giancarlo responsible for welcoming Queen Christina of Sweden, a new convert to Catholicism, to Rome in 1655.[3] Upon discovering of the closeness that had formed between the two, the Pope sent Gian Carlo back to Florence, declaring him "too handsome and too young" to be "spiritual advisor" to the Queen.
Here, Giancarlo led a life of dissipation, taking many mistresses; nevertheless, Ferdinando II delegated to him the management of the state's financial affairs. After one of his mistresses died, "the sexton who buried her said that Cardinal Gian Carlo, remembering the convulsions of that ivory body, came to look once more; and overcome by so much beauty, entered the vault and lay with her for the last time." He murdered a romantic rival, Cavaliere Luna, but his brother, Duke Ferdinando II, did nothing. [4][5] He was patron of science, letters and music. He founded the Accademia degli Immobili and contributed to the construction of Teatro della Pergola and the enrichment of the Galleria Palatina di Palazzo Pitti.[6]
Generations are numbered from the children of Francesco de' Medici, first Grand Duke of Tuscany. Later generations are included but the grand duchy was abolished in 1860.