Complex sentence: His step-nephew, Miltiades the Younger, later became tyrant of the Thracian Chersonese; he was named after his uncle and became famous for his victory over the Persians at Marathon.
Split into simpler sentences: His step-nephew, Miltiades the Younger, later became tyrant of the Thracian Chersonese. Named after his uncle, the junior Miltiades is best known for his victory over the Persians at Marathon.