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 25/25 match between two men who share a surname (or variant) means they likely share a common male ancestor within the genealogical time frame. The probability of a close relationship is very high.
1 Related A 24/25 match between two men who share a surname (or variant) means they likely share a common male ancestor within the genealogical time frame.For most closely related and same surnamed individuals, the mismatch markers are often DYS439, DYS385, DYS389i, DYS389ii, DYS458, DYS459, DYS449, and DYS464, which have shown themselves to move most rapidly.
2 Probably Related A 23/25 match between two men who share a surname (or variant) means they may share a common male ancestor within the genealogical time frame. The probability of a relationship is good. However, your results show mutations and therefore more time between you and the other same surnamed person.For most closely related and same surnamed individuals, the mismatch markers are often DYS439, DYS385, DYS389i, DYS389ii, DYS458, DYS459, DYS449, and DYS464, which have shown themselves to move most rapidly.
3 Probably Not Related A 22/25 match between two men who share a surname (or variant) means they may but are unlikely to share a common male ancestor within the genealogical time frame. The probability of a relationship is poor.If enough time has passed, it is possible that you and another distantly related family members’s line each have had a mutation or perhaps two. The only way to prove that is to test additional family lines and find where the mutation took place. Through further testing, you can find the person in between each of you. This ‘in betweener’ becomes essential for you to find.
4 Not Related A 21/25 match is too far off to be considered related within the genealogical time frame.It is vaguely possible that the rule for “Probably Not Related” applies. The only way to confirm a relationship is to test additional family lines and to find where the mutations took place. By testing additional family lines, you can find the person in between. This ‘in betweener’ is essential for you to find. Without him, it is highly unlikely that the match is genealogical.
5 Not Related A 20/25 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.
6 Not Related A 19/25 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.
>6 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.