Use other clues to determine if the "close enough" person is your ancestor. Is he:
- in the right location?
- acting in a way that is consistent with your ancestor?
- of a close enough age to be your ancestor?
- interacting with known associates of your ancestors?
Even answering all these questions with a "yes" is no guarantee, but it is a good start towards making certain that "close enough" name is really "close enough."