Peter was a medieval Roman noble. Like his father, he carried the title of Romanorum patricius, consul, dux et senator ("Patrician, consul, duke, and senator of the Romans"), implying his secular command over Rome and its militia. He was the son of Alberic III, Count of Tusculum and a descendant of Theophylact I, Count of Tusculum.
Historians use the term Saeculum obscurum to describe the period when the Papacy was under the direct control of the Roman nobility, particularly under the domination of the family of Theophylact, which later became the Colonna family.