Thomas Lincoln was the fourth and youngest son of United States President Abraham Lincoln and his wife, Mary Todd Lincoln. His father gave him the nickname "Tad" while quite young because of the child's predisposition to "wiggling like a tadpole".
Tad was born and photographed with a small fissure on his upper lip just to the left of midline. Although undiagnosed at the time, contemporary documents described Tad by saying "he had a cleft palate and lisped." Twenty-first-century speech/language pathologist, John M. Hutchinson, interprets contemporary photographs and documents regarding Tad, as evidence the child had both communicative and craniofacial deformities. Cleft lip and palate are a phenomenon observed to "run in families". Hutchinson suggests that Tad Lincoln's cleft lip was inherited from his paternal grandfather and namesake who also was photographed with forme fruste of the upper lip on the left side.
He died at age 18 having never married and without children. His death has been attributed to either tuberculosis, pleuristic attack, pneumonia, or congestive heart failure.
Publication: Online publication - Provo, UT, USA: The Generations Network, Inc., 2004.Original data - United States of America, Bureau of the Census. Eighth Census of the United States, 1860. Washington, D.C.: National Archives and Records Administration, 1860. M653, 1