Complex sentence: The family moved, first to Derry City, where his younger brother Dónal was born in 1949, and then Monica and the two boys moved to Cork, where the brothers were raised.
Split into simpler sentences: The family moved, first to Derry City, where his younger brother Dónal was born in 1949. His mother, Monica, and the two boys then moved to Cork, where the brothers were raised.