Christ's Faithful People
The last pope named John was John XV. There had indeed been a man who called himself John XVI, but he was John Philagathus the unfortunate antipope set up by Crescentius II against Pope Gregory V. John XVII, therefore, should have been called John XVI. The reason why John Sicco, who became Pope Sylvester's successor, was called John XVII is not hard to guess. Crescentius III was now Patrician and the real power in Rome; and Crescentius III was the son of Crescentius II who had set up antipope John XVI. Consequently, Crescentius III would naturally insist that the pope whose election he had secured should assume the style of John XVII. Thus his father would be saved from being publicly branded as the supporter of an antipope.
Crescentius III dominated the papacy during this period and carried matters with so high a hand that by one chronicle he is called "the destroyer of the apostolic see." This however, was probably because he usurped the popes' temporal power. As far as can be known, Crescentius III seems to have secured the election of worthy men as popes. John XVII was a Roman named John Sicco. Before he became a priest he had been married and had had three children, all of whom entered the ecclesiastical state. All that is known of his brief pontificate is that he was consecrated on June 13, 1003, and that he died on November 6 of that same year.
John XVII was buried in the Lateran Basilica.