Throughout the centuries Rome has produced a multitude of murderers, mad, corruptible, heretical, incestuous, homosexual, fornicators, masonic, secret agents, teenage and even female popes, not to mention three popes all in office at the same time.   

Some Popes killed one another; others were found dead in brothels; some were known to have raped children and then fled with Rome's purse, only to return later and demand more money. There was even a time when a child of eleven sat in Peter's Chair (De Rosa, pgs. 64-74.)  

"Pope Damasus, whose election to the pontificate was secured by a hundred and thirty-seven murders, authorises persucution of those who speak out against any of the holy canons and adds, 'It is permitted neither to think nor to speak differently from the Roman church' (Grattan Guinness, Romanism and the Reformation, pg. 43.)  

Here's just a brief snap shop of some of these wicked men:

Pope John X (914-928)

When just five, he was made Archbishop and later rose to Pope (Catholic Encyclopaedia, Vol. VIII, pg. 425)

Pope John XI (931-936)

He was the son of Pope Sergius III and his mother later ordained him Pope for his 20th birthday (Catholic Encyclopaedia, Vol. VIII, pg. 426.)

Pope John XVIII (1003)

Another son of a priest (Catholic Encyclopaedia, Vol, VIII, pg. 429.)

Pope Innocent VIII (1484-1492)

Has at least 8 sons by his many mistresses (Catholic Encyclopaedia, Vol. VIII, pgs. 19,20)

Pope Julius (1503-1513)

He is known to have fathered at least 3 daughters (Catholic Encyclopaedia, Vol. VIII, pg. 562.)

Pope Gregory XIII (1572-1585)

This chequered pope masterminded the Massacre of Bartholomew yet he too enjoyed a sordid life, for he was the father of one son (Catholic Encyclopaedia, Vol. VII, pgs. 2,3.)

It should also be pointed out that rich families were able to buy the office of Pope, as this was a very common method of keeping this lavish and powerful position within some Roman families. Religion and reverence for God had nothing to do with it: it was simply a means of controlling a lucrative and influential office within the Catholic church.  

There were even times when several people claimed to be Pope simultaneously. So I do wonder how Rome can boast that they have a successive and uncontaminated chain going right back to Peter? I think they are deluding themselves!