He was the illegitimate son of Frederick II Hohenstaufen and Bianca Lancia. However he was legitimated by his father that is likely married his mother "in articulo mortis". He was crowned King of Sicily against the will of the pope that was supporting Charles of Anjou that prevailed after a long struggle winning and Killing him at the battle of Benevento (Campania, Italy).
Note: "Sicilia" is not a family name, but a title "king of Sicily" that belonged to several families: Altavilla, Hohenstaufen, Anjou, Aragon. Augsburg, Bourbon .