Complex sentence: He married in 1877, Marion, daughter of Thomas Buckland, who survived him with two sons and a daughter, Dorothea Mackellar, who became a famous poet and prose-writer.
Split into simpler sentences: He married in 1877, Marion, daughter of Thomas Buckland, who survived him with two sons and a daughter. His daughter, Dorothea Mackellar, did distinguished work as a poet and prose-writer.