She was the mother of Marozia, alleged concubine to Pope Sergius III, and the mother of Pope John XI, fathered by—according to Liutprand of Cremona and the Liber Pontificalis— Sergius. A third contemporary source, however—the annalist Flodoard (c. 894–966)—says John XI was the brother of Count Alberic II of Spoleto, the latter being the offspring of Marozia and her husband Count Alberic I of Spoleto. Hence John too was probably the son of Marozia and Alberic I.
Theodora was characterized by the aforementioned Liutprand as a "shameless whore ... [who] exercised power on the Roman citizenry like a man". Liutprand, a bishop of Cremona, was described by the Catholic Encyclopedia as frequently being unfair to adversaries and could be partial in his judgments.
- E. Dümmler, Auxilius u. Vulgarius. Quellen und Forschungen zur Geschichte des Papsttums im Anfange des zehnten Jahrhunderts, Leipzig 1866, pp. 12–26;
- P. Fedele, Ricerche per la storia di Roma e del papato al secolo X, in "Archivio della Società Romana di Storia Patria", 33, 1910, pp. 177–247; 34, 1911, pp. 75–115 e 393–423;
- L. Duchesne, Serge III. et Jean XI., in "Mélanges d'archéologie et d'histoire", 33 (1913), pp. 25–64
- Ferdinand Gregorovius, Storia di Roma nel medioevo, New Compton Editori Srl, Roma 1972
- Lexikon des Mittelalters, München 2002
- Daniela Schumacher-Immel (1996). "Theodora, die Ältere". In Bautz, Traugott. Biographisch-Bibliographisches Kirchenlexikon (BBKL) (in German). 11. Herzberg: Bautz. cols. 919–920. ISBN 3-88309-064-6.
- Abbott, Elizabeth (2010). A history of mistresses. London: Duckworth. ISBN 1590208765.
- McCabe, Joseph (200u). Crises in the history of the papacy: a study of twenty famous popes whose careers and whose influence were important in the development of the church and in the history of the world. [Whitefish, Mont.]: Kessinger Publishing. ISBN 0766179044.