The mysterious death of Francesco I de' Medici and Bianca Cappello: an arsenic murder?

Soon after the sudden and simultaneous deaths of Francesco I de’Medici, Grand Duke of Tuscany, and his wife, Bianca Cappello, in October 1587, rumours spread that the two had been murdered by Francesco’s brother, Cardinal Ferdinando. 2 Apparently, Ferdinando had a very good motive to kill his brother and the woman that Francesco had loved and then married after the death of his first wife the Grand Duchess Giovanna of Austria. Ferdinando was at risk of being excluded from the succession if Francesco’s illegitimate son Don Antonio was to inherit the title of Grand Duke or, even worse, if Bianca, who was no longer able to have children, was to falsify the birth of an heir.