Complex sentence: Thomas Medwin (1788--1869) was an early 19th-century English poet and translator known chiefly for his biography of his cousin Percy Bysshe Shelley and for recollections of his close friend Lord Byron.
Split into simpler sentences: Thomas Medwin (1788--1869) was an early 19th-century English poet and translator. He was known chiefly for his biography of his cousin, Percy Bysshe Shelley, and for recollections of a close friend, Lord Byron.