:::::::From Roman history, which is the area I'm most familiar with, any number of people fall into that category. To take an article I happen to have edited recently, how about Ventidius Cumanus, governor of Judaea c. AD 50? He's mentioned by two extant authors, Josephus and Tacitus; both are writing about half a century after the events they're describing, and they're seriously inconsistent with each other. But nothing I read while working on the article suggested any doubts about Cumanus' existence. Some people might conclude that neither Jesus nor Cumanus existed, but in covering either position Wikipedia needs to give an accurate impression of its scholarly popularity.