Genealogists have discovered the two heavyweights, who are atop the polls in America's leading parties the Republicans and Democrats, are 19th cousins.
Trump and Clinton, who were once friends, are both related to the Duke and Duchess of Lancaster - their 18th grandparents.
MyHeritage.com and Genie.com researchers tell news show Extra the two politicians' their 19th great-grandfather was King Edward III.
Author A.J. Jacobs, who helped with the research, says, "There is precedent for ruling a country; it's in their genes."