Girolamo Riario was NOT killed in Rome after the selection of Innocent VIII as Pope. He was assassinated five years later in the city of Forli, one of his possessions, on 14 April 1488, by two of the noblemen of Forli, the Orsi brothers. His wife, Caterina Sforza Riario who no hand in his assassination and hunted down and executed those who did have a hand in it.
Girolamo Riario and Caterina Sforza Riario had six children together prior to his death. In 1497 Caterina married Giovanni de' Medici, a grandson of Lorenzo de' Medici, the brother of Cosimo de' Medici in Season 1. They had one child and Caterina's grandson as a result of this marriage was Cosimo de' Medici, a.k.a. Cosimo I, Grand Duke of Tuscany.
Pope Innocent VIII was succeeded in 1492 by Pope Alexander VI, formerly known as Rodrigo Borgia.
Guilio was originally intended to go into the Army, but only took Holy Orders as a priest AFTER Lorenzo's death.