Complex sentence: Grant was the last LDS church president to have practiced plural marriage, having had three wives, though by the time he became church president in 1918 only his second wife, Augusta Winters, was still living.
Split into simpler sentences: Grant was the last LDS Church president to have practiced plural marriage. He had three wives, though by the time he became church president in 1918 only his second wife, Augusta Winters, was still living.