Principality of Taranto
In 1335, William married María Álvarez de Jérica, a descendant of Roger of Lauria, without papal dispensation, as both John XXII and Benedict XII wanted to check the power of Frederick his father. Two years later, his father willed him the Principality of Taranto, the county of Calatafimi, the honour of Monte Sant'Angelo, and various castles and lands in Noto, Spaccaforno, Capo Passero, and Avola when his mother, Eleanor, daughter of Charles II of Naples, died. She died in 1341, but William died first on 22 August 1338. He left his library to the Dominicans of Palermo and was buried in the cathedral there.