Bianca de' Medici is the sister of Lorenzo the Magnificent and Giuliano de' Medici.
When Lorenzo takes over the power from his father, he promises Bianca's hand in marriage to Bastiano Soderini.
When Bianca finds out about the engagement through Bastiano, she confronts Lorenzo. He explains that they both have the duty to marry whether it is their choice or not. She explains that she loves another, Guglielmo de' Pazzi.
In childhood, she and Guglielmo were bound to be married until Jacopo de' Pazzi broke off the engagement.
She and Guglielmo run away together in where he takes her virginity, therefore bounding them together by God. When returned back the court by the guards, Lorenzo decides to make a deal with Jacopo to officially marry Guglielmo and Bianca due to Bianca's resistance. In doing so, Jacopo agrees but disowns Guglielmo as a Pazzi.
Lorenzo however makes a new deal regarding the banking affairs with the Soderinis, who upon learning of their son Bastiano's marriage being called off were quite in despair.
Later Bianca gives birth to a daughter named Contessina. When Jacopo and Francesco Pazzi scheme to murder the Medici brothers, they try to intimidate Guglielmo of their intentions, but being true to his wife Bianca and her family, Guglielmo does not listen to them, thus he and Bianca were unaware of the assault that was to be held on Easter against the Medici.
After the murder of his beloved brother, an enraged Lorenzo tries to kill Guglielmo but believing his innocence, Bianca defends her husband and upon him being ordered to be banished from Florence by Lorenzo, Bianca leaves her family forever to be with Guglielmo.