Complex sentence: Gaunt's brother Guy Reginald Gaunt, was also an Admiral and Knighted, his sister Mary Elizabeth Bakewell Gaunt was a well known author in her native Australia and wrote several travel books.
Split into simpler sentences: Gaunt's brother Guy Reginald Gaunt, was also an admiral. Their sister, Mary Elizabeth Bakewell Gaunt, was a well known author in her native Australia and wrote several travel books.