The casual student of Lincoln probably doesn't realize that many of his wife's family members fought for the Confederacy during the Civil War. This article describes in brief detail some of Lincoln's in-laws who fought for the South.
Throughout the Civil War, it was rumored in Washington that Mary Todd Lincoln was actually a sympathizer and spy for the Confederacy. A congressional committee was established to investigate these rumors, in turn leading to an extraordinary unannounced appearance by Lincoln at the committee hearings. He denied the rumors with such force, but tinged with sadness, that the committee quietly suspended its investigations of Mrs. Lincoln.