Complex sentence: His first cousins the Turnbull family were the last of the "First Family" during the Siege of Petersburg, and was the residence of Robert E. Lee for the last 13 weeks of the war.
Split into simpler sentences: His first cousins the Turnbull Family were the last of the "First Family" during the Siege of Petersburg, and was the residance of Robert. E Lee for the last 13 weeks of the war.