She was a daughter of Bohemund V of Antioch and his second spouse, the Italian noblewoman Lucienne of Segni, a relative of Pope Innocent III.
The official King of Jerusalem at the time was the absentee Conrad of Hohenstaufen, who died in 1254, with his title passing to his son Conradin, also still in Germany.
The dispute, however, continued and Pope Alexander IV sent the Genoese to attempt to settle it; John of Jaffa convinced Bohemund and Plaisance to unite Jerusalem, Antioch, and Tripoli against them.
In 1260 the high cleric (a future pope) Jacques Pantaleon arrived to take up the vacant patriarchate, hoping to solve the crisis.
Pope Urban may have issued a papal bull to Plaisance expressing his disapproval of her relationship, Audi filia et.