After the death of his father Adalbert II in 915, he was the Count and Duke of Lucca and Margrave of Tuscany until his own death in 928 or 929. His mother Bertha was his regent from his father's death until 916.
In order to counter the influence of Pope John X (whom the hostile chronicler Liutprand of Cremona alleges was one of Marozia's lovers), Marozia subsequently married his opponent Guy of Tuscany, who loved his beautiful wife as much as he loved power. Together they attacked Rome, arrested Pope John X in the Lateran, and jailed him in the Castel Sant'Angelo. Either Guy had him smothered with a pillow in 928 or he simply died, perhaps from neglect or ill treatment. Marozia seized power in Rome in a coup d'état. Guy died 3 February 929.
He had one daughter, Theodora (or Bertha), and probably a few other children of which nothing else is known. None of his children survived him and when he died in 928 or 929 his brother Lambert succeeded him as count and duke of Lucca and margrave of Tuscany. Meaning that either this page is incorrect or the page listing "his son" Adalberto the Margrave (died 951, was elevated to the nobiliary title of "Visconte" in 940) is incorrect.[circular reference]
- Townsend, Geo (1847) Ecclesiastical and Civil History Philosophically Considered, Vol. II, p. 157
- Mann, Horace K., The Lives of the Popes in the Early Middle Ages, Vol. IV: The Popes in the Days of Feudal Anarchy, 891-999 (1910). pp.163-164.
- Adalberto the Margrave