Complex sentence: His older brother Thomas Biddle, a War of 1812 hero who died in a duel, should not be confused with his cousin by the same name, who became a leading exchange broker in Philadelphia.
Split into simpler sentences: His older brother Thomas Biddle was a War of 1812 hero who died in a duel. His brother, Thomas, should not be confused with his cousin by the same name, who became a leading exchange broker in Philadelphia.