John was a Roman by birth, and was in fact the son of Marouzia, essentially the ruler of Rome at the time. It’s unclear whether John’s father was Alberic I, Marouzia’s first husband, or Pope Sergius III, who some believe had an affair with John’s mother years before. By all accounts, John XI was placed in office as a pawn of Marouzia’s to further extend her own ambitions. John sanctioned an unpopular -- and, by the day’s standards, incestuous -- marriage between his mother and Hugh, her brother-in-law and king of Italy. The marriage sparked a war between John XI’s new stepdad and his younger half-brother, Alberic II, which ended in Alberic throwing mom in prison and banishing Hugh from Rome. That’s one way to say, “You’re not the boss of me.” John, never having had much real power of his own, died in late 935, having reigned the better part of five years. 

When St. Odo, abbot of the great Benedictine monastery at Cluny, wished to reform nearby abbeys in France and Italy, it was Pope John XI who gave the go-ahead. Thus John was best known, perhaps ironically, for laying the groundwork of monastic reform that would eventually help to cleanse the very papacy itself. 

Fun fact: If indeed John XI was the son of Sergius III, that would make him the only illegitimate son of a pope to become pope himself.