[1] Definitive unification occurred in 1816, when Ferdinand IV and III made the two entities into a single state, the Kingdom of the Two Sicilies.
The Kingdom of Sicily, which by then comprised not only the island, but also the southern third of the Italian peninsula, rapidly expanded itself to include Malta and the Mahdia, the latter if only briefly.
Constance was married to the Emperor Henry VI and he pressed his claim to the kingdom from William II's death, but only succeeded in displacing his wife's family in 1194.
There is evidence that, during the baronial revolt of 1197, there was an attempt to make Count Jordan Lupin of Bovino king in opposition to Henry VI.
Manfred was regent of Sicily for his nephew, the child Conrad II ("Conradin"), but took the crown in 1258, and continued to fight to keep the kingdom under the Hohenstaufen.
In 1262 the pope reversed his previous decision and granted the kingdom to the King of France's brother, Charles of Anjou, who succeeded in dispossessing Manfred in 1266.