Complex sentence: She was the eldest child of three born to Ida Castledine (née Armstrong) and Walter Cecil Castledine, who worked as an electrical engineer employed by British Coal to oversee work at coal mines including Kiveton Park Colliery.
Split into simpler sentences: She was the eldest child of three born to Mrs Ida Castledine (née Armstrong) and Mr Walter Cecil Castledine. Castledine's father, Cecil, worked as an electrical engineer employed by British Coal to oversee work at coal mines including Kiveton Park Colliery.