Prior to Benedict XVI there were 14 other popes with that name. Pope Benedict X was an antipope and does not count.
His name was Cardinal Joseph Alois Ratzinger.
Joseph Alois Ratzinger was his original name.
The full name of Pope Benedict XVI before he changed it was Joseph Alois Ratzinger.
Joseph Alois Ratzinger
Pope Benedict's first name is Joseph.
There have been 15 popes named Benedict. There was no pope named Benedict X. That name was chosen by an anti-pope who was not a true pope. Pope Benedict XI should have taken the name Benedict X but, due to some confusion, he did not. At the time of Benedict's election, however, this status was not recognized, thus the man the Roman Catholic Church officially considers the tenth true Pope Benedict took the official number XI rather than X. This has advanced the numbering of all subsequent Popes Benedict by one. Popes Benedict XI-XVI are, from an official point of view, the tenth through fifteenth popes by that name.
Pope Benedict XVI is the only pope with the name of Josef Ratzinger.
Maria Ratzinger was the name of Pope Benedict's mother.
Pope Benedict was able to choose a new name when he was elected Pope. Popes usually choose the name of a saint they admire.
Pope Emeritus Benedict XVI
Which Pope Benedict? There have been 16 popes by that name.