Son of Peter III of Aragon and Constance of Swabia (daughter of Manfred), Frederick III was named as if to follow in the footsteps of the two Holy Roman Emperors, Frederick I and Frederick II. At the death of Peter III in 1285, the kingdom of Aragon was willed to Frederick's oldest brother, Alfonso III, and the Kingdom of Sicily fell to his second born, James II. When Alfonso died in 1291, James also inherited the Aragonese crown, and left Sicily to reside in Aragon, appointing Frederick as his regent.
A peace process which had been underway between James II of Sicily and Charles II of Naples resulted in a 1285 treaty by which James would renounce his claim to the Sicilian island in favor of the Pope, and would restore the mainland portions of Sicily to Charles. Not willing to accept the treaty, members of the Sicilian parliament crowned Frederick as King in November of 1285. A prolonged war with Naples and the papacy produced no real political effects, and the 1302 Peace of Caltabellotta stipulated that Frederick would retain the island of Sicily as "King of Trinacria" until his death, at which point it would return to Angevin control. After 1311, Frederick was able to take advantage of the presence of the new Emperor Henry VII in Italy, creating an alliance against Naples. Although he eventually succeeded in assuring the continuance of Aragonese rule in Sicily, Frederick achieved it at the expense of decades of war which greatly depleted his kingdom's resources. Frederick was never able to reunite Sicily's island and mainland territories.
Frederick III of Aragon appears in the fifth tale of Day II of the Decameron, defending himself from the plots of the Angevin sympathizers in Sicily. In the sixth tale of Day Five, he is presented as somewhat immature in his proud and impetuous attitude. He nearly causes the unjust death of a relative of Gianni Procida, one of his father's most trusted servants and his father's most faithful admiral. In this tale, Ruggiero di Lauria gives Frederick a lesson in gratitude and humility. It is possible that this quite uncomplimentary portrait is intended to retrospectively explain the disaffection of both men to the Angevin side.
(R.P./N.S.) Fodale, Salvatore. s.v. Federico III (II) d'Aragona. Vol. 45. Dizionario biografico degli italiani. Roma: Istituto della Enciclopedia italiana, 1960. pp. 682-694.