Dubois was of part French-Canadian descent. His paternal grandfather, Toussaint Dubois, was an immigrant who distinguished himself at the Battle of Tippecanoe. His surname was pronounced "deh-bwah" and he was said to have "hated it" when people pronounced the "-bois" suffix as "boys," which he found "insufferable." Dubois' father, Jesse Kilgore Dubois, was an official at the U.S. Land Office in Palestine, Illinois, a former judge and state legislator, an early supporter of the Republican Party, and a close friend of fellow Illinois Republican Abraham Lincoln. In 1856 the elder Dubois was elected Illinois state auditor and moved the family to the state capital, Springfield.
