The younger Ptolemy entered the political scene of central Italy for the first time in 1117, when he appears as joint count with his father and is given in marriage to Bertha, illegitimate daughter of Henry V, Holy Roman Emperor.
The counts were also confirmed in their possession of all the territory of the Consul Gregory, Ptolemy I's grandfather.
On 8 April 1149, Pope Eugene III took refuge in Ptolemy's Tusculuan fortress.
At that time, Louis VII of France stopped in Tusculum on return from the Second Crusade.
Ptolemy did leave another son, named Jordan, who settled in Gavignano in Volscia after the destruction of Tusculum in 1191.