But Sotos says the key piece of evidence lies in Lincoln's family. "It is the Lincoln children who make me very confident," he said. Three of Lincoln's sons died young. Each had bumpy lips.

How else to explain what came to light when, more than a century later, scholars discovered an unknown trove of Lincoln family pictures long in the possession of the president’s descendants?

In a remote corner of the Ozark Mountains in Arkansas, I found a man whose mother, a cousin of Lincoln, had passed her childhood with him in his father's family, and had preserved a store of ...

But Sotos says the key piece of evidence lies in Lincoln's family. "It is the Lincoln children who make me very confident," he said. Three of Lincoln's sons died young. Each had bumpy lips.