Pope Sergius III had young girl as mistress
Sergius III became pope in 904. Theophylact, the Count of Tusculum, controlled Rome. Theophylact's daughter, Marozia, a young girl of 12 or 13, became the pope's mistress. Marozia became pregnant and bore the Roman bishop a son. Sergius died in 911. In 927, Marozia, Sergius's mistress, controlled Rome. Marozia arrested Pope John IX (914-928) and put out his eyes. She then threw him in prison where he died in 928. Marozia appointed the next three popes, one of them her illegitimate son by Sergius. This pope took the name John XI (931-935). In an effort to cement her control of Rome, Marozia murdered her husband in 932 and married another nobleman. Alberic, her son by her murdered husband, overthrew his mother and assumed control. He successfully ruled Rome from 932-954. As his death neared he forced the Roman senate to appoint his son, Octavian, pope in 955. Octavian takes the name John XII and begins his rule.
source: Article 'The medieval papacy'; www.christianchronicler.com/history1/medieval_papacy.html; Taken from website: 15 January 2005