Complex sentence: Breckinridge studied education at a classical school operated by Dr. Louis Marshall, the brother of Chief Justice John Marshall, then followed his brothers, Cabell and John, to Princeton in 1817.
Split into simpler sentences: Breckinridge studied education at a classical school operated by Dr. Louis Marshall, the brother of Chief Justice John Marshall. Breckinridge followed his brothers, Cabell and John, to Princeton in 1817.