Complex sentence: Andronikos is first mentioned during the siege of Corfu in winter 1148/49, headed by his father Stephen, in an attempt to expel the Normans of the Kingdom of Sicily who held the city.
Split into simpler sentences: Andronikos is first mentioned during the siege of Corfu in winter 1148/49. The Byzantine forces, led by his father Stephen, were attempting to expel the Normans of the Kingdom of Sicily who held the city.