After the argument between Michael Corleone and the members of the Vatican, he leaves the building, saying, “We’re back with the Borgias”. Mario Puzo, author of The Godfather, later wrote a book about the Borgias called ‘The Family’. It was later revealed, during the broadcast of the television series The Borgias, that the Borgias were the original inspiration for the Corleones. Vito was based on Rodrigo Borgia, AKA Pope Alexander VI. Michael was based on Cesare Borgia, Santino on Juan Borgia, Fredo on Gioffre Borgia, and Connie on Lucrezia Borgia. (x)
Know this, Lucrezia. My death frees you of all bonds to the past. Dearest soul, live. Live today, live for the days to come. Forgive Rodrigo, Juan, your ridiculous Cesare. Forgive us one last time, so that we, too, may be free. I kiss your hand. I kiss your lips. Wherever forever is, I will love you.
Almost any explanation is possible, for Borgia, behind his open, affable front, could be as close and secretive as a peasant. There were certain matters about his family that he did not want the world to learn of, and the world never did learn of them, despite the endless probings first of enemies and then of generations of scholars. The greatest mystery stemmed from precisely this ability of the Borgia family to keep its secrets to itself. Few families in Italy or for that matter in all Europe attracted such wide, sustained and detailed attention as did the four children of Rodrigo Borgia by Vanozza Catanei. Cesare, Juan, Lucrezia, Joffre -each in turn came under a scrutiny that ranged from the bitterly hostile to the coldly legal, expressed not only in the ferocious satire of political enemies but also in the precise statements of lawyers. […]Nevertheless, despite this enduring interest, despite the swarms of courtiers and ambassadors who surrounded the family for some twenty years and who were paid to ferret out every last detail about its members, despite the profuse legal documentation, the relationship of these Borgias one with another remains rooted in obscurity.
E.R Chamberlin - The Fall of the House of Borgia