Unfortunately, having discovered these ready sources of revenue, he continued to exploit them for purposes far less easy to condone.
As a nepotist Sixtus was almost unsurpassed in the history of the Papacy.

Four of his nephews and their aggrandizement were the particular objects of his attentions, and two of these--as we have already said--Piero and Girolamo Riario, were universally recognized to be his sons.
Piero, who was a simple friar of twenty-six years of age at the time that his father became Pope, was given the Archbishopric of Florence, made Patriarch of Constantinople, and created Cardinal to the title of San Sisto, with a revenue of 60,000 crowns.
We have it on the word of Cardinal Ammanati( 1)--the same gentleman who, with Roderigo de Lanzol y Borja made so scandalously merry in de Bichis' garden at Siena--that Cardinal Riario's luxury "exceeded all that had been displayed by our forefathers or that can even be imagined by our descendants"; and Macchiavelli tells us( 2) that "although of very low origin and mean rearing, no sooner had he obtained the scarlet hat than he displayed a pride and ambition so vast that the Pontificate seemed too small for him, and he gave a feast in Rome which would have appeared extraordinary even for a king, the expense exceeding 20,000 florins." 1 In a letter to Francesco Gonzaga.
2 Istorie Florentine.
Knowing so much, it is not difficult to understand that in one year or less he should have dissipated 200,000 florins, and found himself in debt to the extent of a further 60,000.
In 1473, Sixtus being at the time all but at war with Florence, this Cardinal Riario visited Venice and Milan.

In the latter State he was planning with Duke Galeazzo Maria that the latter should become King of Lombardy, and then assist him with money and troops to master Rome and ascend the Papal Throne--which, it appears, Sixtus was quite willing to yield to him--thus putting the Papacy on a hereditary basis like any other secular State.
It is as well, perhaps, that he should have died on his return to Rome in January of 1474--worn out by his excesses and debaucheries, say some; of poison administered by the Venetians, say others--leaving a mass of debts, contracted in his transactions with the World, the Flesh, and the Devil, to be cleared up by the Vicar of Christ.
His brother Girolamo, meanwhile, had married Caterina Sforza, a natural daughter of Duke Galeazzo Maria.

She brought him as her dowry the City of Imola, and in addition to this he received from his Holiness the City of Forli, to which end the Ordelaffi were dispossessed of it.

Here again we have a papal attempt to found a family dynasty, and an attempt that might have been carried further under circumstances more propitious and had not Death come to check their schemes.
The only one of the four "nephews" of Sixtus--and to this one was imputed no nearer kinship--who was destined to make any lasting mark in history was Giuliano della Rovere.