Complex sentence: In 1154, Roger II died and the kingdom of Sicily passed to his fourth son, William I. William dispossessed his half-brother Simon immediately, claiming that Taranto was too important a fief to go to an illegitimate son.
Split into simpler sentences: In 1154, the elder Roger died and the kingdom of Sicily passed to his fourth son William. This William dispossessed his half-brother Simon immediately, claiming that Taranto was too important a fief to go to an illegitimate son.