Mary Todd Lincoln's father was Robert Smith Todd (1791 - 1849) and was a slave owner.

Her mother was Elizabeth Ann Parker Todd (1794 - 1825)

When her mother died her father married Elizabeth L Humphreys Todd (1800 - 1874)

Mary Todd Lincoln's half brothers served with the Confederacy and they were:

Private Samuel B. Todd served with Company H of the Crescent Louisiana Regiment and killed at Shiloh. (not with the 24th Louisiana as previously mentioned)

Captain Alexander Humphrey's Todd killed in action at Baton Rouge, Louisiana on August 5, 1862.

Captain David Humphrey's Todd served in Company A of the 21st Louisiana (Patton's) and survived the war.

Dr. George Rogers Clark Todd served as surgeon in the Confederate Army and survived the war.

Charles Henry Kellogg Senior married Margaret Todd. A southern sympathizer he survived the war.

Benjamin Hardin Helm married Emilie Pariet Todd, he was killed at the Battle of Chickamauga.

Captain Nathaniel Henry Rhodes Dawson married Elodie Breck Todd and he served in Company C of the 4th Alabama Infantry and survived the war.

William Wallace Herr married Catherine Bodley Todd and he served in a Confederate Kentucky unit during the war and survived the war.

None of Mary Todd Lincoln's half brothers or brothers served in the Union Army and likewise none of Mary's half sisters or sister married men that served in the Union Army.