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Okay, so I've asked this question before and it went nowhere. I think it didn't even make it past my original question.

Bianca Cappello (1548-1587) was a Venetian beauty, a descendant of the Morosoni family, who fell in love with a Florentine clerk - according to some accounts "a mattress-maker" - married him and eloped to Tuscany. However, she didn't get on well with her in-laws (a sticking trait apparently), and when the unhappy beauty attracted the interest of the Grand Prince Francesco, she became his mistress.

Francesco was already married to Johanna of Austria (whom the Florentines disliked because of her foreigness and also because of her haughtiness), who managed to give him two sons (Filippo, who died in infancy, and one who died at birth, killing his mother too). After Johanna died, Francesco married Bianca (it wasn't an entirely unprecedented step, his father had married Camilla Martelli - his mistress). Well, if the Florentines had disliked Johanna, they despised Bianca, since a rhyme ran around at the time of the wedding "the grand duke has married a Venetian lady/a whore". Venice, however, who had previously tried to extradite her from Tuscany, now changed tune and saw her instead as a boon to improve Tuscan-Venetian relations.

Bianca was under pressure from the start to deliver the goods in the form of a male heir. There was a child - Antonio (1576-1621) - who Bianca said was Francesco's, but everyone else in his family said was a changeling. Many interpret the fact that Francesco only named Antonio as his own child after Johanna's death a sign that he did not truly believe it was his child. Except that Johanna's father and brother were the Holy Roman Emperors, her cousin the king of Spain - and you wouldn't want to exactly piss off team Hapsburg at that point. The boy was naturalized when Francesco married Bianca after

However, even D. Felipe II approved the legitimization/naturalization of Antonio as successor in 1584. And then it all went horribly wrong. Bianca and Francesco both died - presumably poisoned by his brother, Cardinal Ferdinando de Medici. Suddenly, Bianca's recent phantom pregnancy was cited as proof that Antonio was a changeling due to the fact that her pregnancy in 1576 was also phantom. And Ferdinando, shucking his cardinal's skirts, climbed onto the throne.

Antonio was forced into the Order of Malta by Ferdinando (as a way of ensuring no heirs would be born to his "claim" to Tuscany). Except Antonio had five illegitimate children - three boys, two girls.

Now, the evidence is there that it was malaria rather than poisoning that killed the grand duke and duchess. So, what if one, or both of them, were to survive the malaria? How would Tuscany's future be different?
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