If your ancestor signs a deed, find out how old he had to be to execute that document. If an ancestor is on a tax list, does it mean he owned real property, was above a certain age, perhaps even under a certain age. Some records seem to tell very little. If that appears to be the case, find out as much as you can about why the document was created, who was "eligible" to be on the document, if the order of the names has any significance, etc.
There may be clues you are not seeing!