Complex sentence: His older brother, Ephraim Kirby Smith, a captain in the regular army, served with him in the 5th U.S. Infantry in both the campaign with Taylor and Scott, until he died from wounds suffered at the Battle of Molino del Rey in 1847.
Split into simpler sentences: His older brother, Ephraim Kirby Smith, a captain in the regular army, served with him in the 5th U.S. Infantry in the campaigns with both Taylor and Scott. Ephraim died from wounds suffered at the Battle of Molino del Rey in 1847.