Nothing about the life story of Benedict IX indicates that he was ever suited in any way for service in the clergy, let alone the responsibility of serving as pontiff.
The Tusculani family had achieved notable power in Rome, displacing the Crescentii, who had previously been instrumental in putting several popes into office. Teofilatto's uncle, also named Teofilatto, had been the first Tusculani pope, installed by force, and had taken the name of Pope Benedict VIII. Teofilatto's other uncle, Romano, succeeded Benedict VIII as John XIX. Teofilatto's father, Count Alberic of Tusculum, who was the brother of these two popes, placed his son on the papal chair in October, 1032.
Teofilatto Tusculani was probably born sometime in 1012 C.E. This date is extrapolated from his ascension to the papal throne in 1032, when he is believed to have been about 20 and possibly as young as 19 years of age. A contemporary chronicler, Raoul Glaber, recorded his age on becoming pope as 12, but most scholars have dismissed this bit of hearsay as unsubstantiated. (Author and historian Reginald Lane Poole called Glaber "not only the most credulous but the most careless and inaccurate of writers.") The official actions Benedict IX took as pope would reasonably preclude the possibility that he was still a child.
There is little direct evidence concerning the details of Benedict IX's pontificate. We do know that he held two, possibly three, synods in Rome. In 1036, he appears to have been the target of an assassination attempt, and he fled the city; he was restored to the throne by Emperor Conrad II. In 1037 he met with the emperor and excommunicated Heribert, Archbishop of Milan, with whom he'd been at odds. In 1038, he put the abbey of Monte Cassino under papal protection. He is known to have directed Bretislav, Duke of Bohemia, to found a monastery as penance for having taken the body of St. Adalbert and held it for ransom.
The details of Benedict's private life are scarce, as well, but there is quite a bit of gossip and general accusations of bad behavior. It's important to note that most of these items are first recorded decades, even centuries, after Benedict's pontificate, and by authors whose interests rested with Benedict's political opponents or, in the case of much later writers, who sought to paint the papacy itself in a bad light. In these sources, Benedict has been depicted as stealing, holding orgies, raping young girls and boys, and committing murder. Unfortunately for those who are looking for scandals, there is no proof of any of these crimes.
This does not mean that Benedict was a saint -- far from it. During his pontificate he was known to be living life to the hilt. He probably had mistresses, allowed duels and other physical conflicts, and indulged himself in all manner of behavior inappropriate for any cleric, let alone the pope. His licentiousness and violence had become notorious enough for the Romans to revolt against him in 1044. This has usually been depicted as "the people" rising up against him, but it is far more likely that the revolt was engineered by opponents of the Tusculani. Still, they had good cause.
When the revolt took place, Benedict wisely turned tail and ran away from Rome. While he was away, John, Bishop of Sabina, was installed as the antipope Sylvester III. Benedict's brothers succeeded in kicking Sylvester out of Rome, and in January, 1045, Benedict returned to take up the papal chair again.
But now Benedict decided he didn't want to continue as pope. Once again, evidence is scarce for why he wanted to leave. There has been some discussion over the possibility that Benedict wanted to marry. The earliest source for this appears to be Bonizo of Sutri, a bishop who wrote the Liber ad Amicum in 1085 so that he might gain the favor and protection of Countess Matilda of Tuscany during the conflict between Pope Gregory VII and Emperor Henry IV. In his book, Bonizo maintained that Benedict wanted to marry his own cousin, and that her father, Gerard de Saxo, would not give her hand in marriage until Benedict renounced the papacy. The veracity of this anecdote is suspect; Bonizo had probably not yet been born in 1045, and there appears to be no other documentary evidence to support the claim.
Whatever his reasons, Benedict apparently sought the counsel of his godfather, Giovanni Graziano, (John of Gratian), who was a priest. Here scholars are on firmer ground. Although libeled by his opponents, Graziano is almost universally regarded by scholars as a decent Christian who had the best interests of the church at heart, and he was evidently so concerned for the future of the papacy under Benedict that he raised a considerable amount of money to pay the younger man to leave. Benedict accepted the substantial payment and resigned in May, 1045; in this way, he became the pope known for selling the papacy.
Graziano took the name of Gregory VI and did his best to right some of the wrongs perpetrated during Benedict's pontificate. But he had little more than a year to do anything before Benedict changed his mind and came back to Rome. (Bonizo maintains that Gerard de Saxo refused to give him his daughter's hand in marriage after all.) At the same time, Sylvester returned to Rome, as well. Both former popes claimed to be the real pope, and attempts were made to oust Gregory.
An appeal was made to the German king by high-ranking citizens of Rome and concerned clergy. Henry III, who was a pious Christian and hoped to be crowned Holy Roman Emperor soon, gladly put together an armed escort and marched south into Italy. He convoked a council at Sutri, which Benedict did not attend. Sylvester did attend and, because he had been elected pope when the sitting pope (Benedict) had neither formally resigned nor been properly deposed, he was deemed a false claimant to the papacy. He was then deprived of all clerical offices and sent to live in a monastery for the rest of his life. Because Benedict had voluntarily resigned, he was officially deposed, in absentia. And because Gregory had paid Benedict to leave -- an act that could be viewed as simony -- he agreed to resign.
A new pope was elected: Suidger, Bishop of Bainberg, took the chair as Pope Clement II. Gregory went to Germany with Henry, who had been crowned Emperor by the new pope, and died several months later.
But this was not the end of Benedict IX. When Clement died less than a year after ascending to the papal throne, Benedict return to Rome and, on November 8, 1047, installed himself as pope one last time. This time his papacy lasted eight months before Henry ordered his removal (a feat accomplished by Boniface of Tuscany on July 17, 1048). The next pope, Damasus II, was chosen by Henry.
What happened next to Benedict is not clear. He is believed to have lived for another 7 years or so, and to have died, in 1055 or 1056, in the monastery of Grottaferrata -- where, surprisingly, he may have entered as a penitent.