Think about the age(s) at which your ancestor marries, buys or sells land, pays taxes, witnesses documents, etc.
Are those typical ages for those things? Or is someone marrying at the age of 14 or marrying at the age of 54 (for the first time)? A ten year old is not witnessing documents.
Use the age as a clue.
And if the age means something is "off" it could be that you have the wrong year of birth to begin with or that there was more than one person with the same name, they were just different ages.