John XVII was nominated to the papacy by [[John Crescentius]], a Roman noble who held power in the city in opposition to Emperor [[Otto III]] (983–1002). John XVII's successor, [[Pope John XVIII]] (1004–09), was also selected by Crescentius.
The previous legitimate Pope John is generally considered to be [[John XV]] (985–996). [[John XVI]] (997–998) was an [[antipope]], according to conventional wisdom, and thus his regnal number XVI should have been reused. But this did not occur, and the sequencing has never been corrected. Also, since there was never a Pope John XX, this means there have only been 21 legitimate Popes named John, not 23 as the regnal number of [[Pope John XXIII]] (1958–63) would suggest. But some historians (at the request of [[Pope John XXI]]), however, often called him Pope John XVIII or "John XVII (XVIII)" due to the legend of another Pope John between Pope John XIV and the true Pope John XV (whom historians sometimes thus called XVI). This legend of a pope between John XIV and John XV, and the antipapacy of John XVI, is why there is so much confusion of the numbering of Popes John, and why the sequence of Johns is now two off.
