In cultures where surnames are passed from father to son, there is additional evidence beyond a DNA match that two men who share a surname are related. Y-chromosome DNA (Y-DNA) test results should be interpreted based on both this information and the actual results.

Genetic Distance Relationship Interpretation
0 Related A perfect 12/12 match between two men who share a common surname (or variant) means they likely share a common male ancestor within the genealogical time frame. The combination of these facts demonstrates their relatedness.However, if the surname is one of the most common (trades or towns), i.e., Smith, Tailor, Miller, etc., then we suggest you utilize additional markers to eliminate the possibility of a coincidental surname and genetic match.
1 Possibly Related An 11/12 match between two men who share a common surname (or variant) means they may share a common male ancestor within the genealogical time frame. To ensure that the match is authentic, you should utilize additional markers.For most closely related or same surnamed individuals, the mismatch markers are likely to be DYS439, DYS385, DYS389I, or DYS389II.
2 Probably Not Related A 10/12 match between two men who share a common surname (or variant) means they are unlikely to share a common male ancestor within the genealogical time frame. To ensure that the match is authentic, you should utilize additional markers.There are two ways with DNA testing to confirm or deny the relationship. One is to test additional family members to search for a line that shows a mutation that is one point closer. The other is to test additional markers. Testing additional markers greatly enhances science’s ability to determine relatedness geared towards the most accurate assessment of the number of generations to a shared ancestor. Only by further testing can you find the person in between each of you. This in ‘betweener’ becomes essential for you to find, and in their absence, we feel you are not related.
3 Not Related A 9/12 match is too far off to be considered related within the genealogical time frame. It is unlikely but vaguely possible that the rule for Probably Not Related applies.
4 Not Related An 8/12 match precludes a relationship within the genealogical time frame. The odds greatly favor that the two men have not shared a common male ancestor within thousands of years.
5 Not Related A 7/12 match between two people means they are not related within the genealogical time frame. The odds greatly favor that the two men have not shared a common male ancestor within thousands of years.
>5 Not Related The two men are totally unrelated within the genealogical time frame on their direct paternal line. Their shared ancestry is deeply anthropological and dates to the common African heritage of the human race.