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 Very Tightly Related A 67/67 match between two men who share a common surname (or variant) means they share a common male ancestor within the genealogical time frame. Their relatedness is extremely close. All confidence levels are well within the time frame that surnames were adopted in Western Europe with the common ancestor predicted, 50% of the time, in three generations or less and with a 90% probability within five generations. Very few people achieve this close level of a match.
1 or 2 Tightly Related A 65/67 or 66/67 match between two men who share the same surname (or a variant) indicates a close relationship. It is most likely that they matched 36/37 or 37/37 on a previous Y-DNA test. Very few people achieve this close level of a match. All confidence levels are well within the time frame that surnames were adopted in Western Europe.
3 or 4 Related A 63/67 or 64/67 match between two men who share the same surname (or a variant) means that they are likely to share a common ancestor within the genealogical time frame. The common ancestor is probably not extremely recent but is likely within the range of most well-established surname lineages in Western Europe. It is most likely that they matched 24/25, 36/37, or 37/37 on previous Y-DNA tests, and mismatches are within DYS458, DYS459, DYS449, DYS464, DYS576, DYS570, and CDY.
5 or 6 Related A 61/67 or 62/67 match between two men who share the same surname (or a variant) means that they may to share a common ancestor within the genealogical time frame. The common ancestor is probably not recent, but may still be within the range of most well-established surname lineages in Western Europe. It is most likely that they matched 24/25, 36/37 or 37/37 on previous Y-DNA tests. Mismatches are within DYS458, DYS459, DYS449, DYS464, DYS576, DYS570, and CDY.
7 Probably Related A 60/67 match between two men who share the same surname (or a variant) means that they may share a common ancestor within the genealogical time frame. Because of the volatility within some of the markers, this is about the same as being 11/12, and it is most likely that they matched 23/25 or 24/25 or 33-34/37 on previous Y-DNA tests. If they test additional individuals, they will most likely find that their DNA falls in between the persons who are seven apart demonstrating relatedness within this family cluster or haplotype. If several or many generations have passed, it is likely that these two lines are related through distant family lines. The only way to confirm the relationship is to test additional family lines and to find where the mutations took place. By testing additional family members, you can find the person in between them. This ‘in betweener’ is essential, and without him, the possibility of a match exists but cannot be confirmed.
8 or 9 Only Possibly Related A 58/67 or 59/67 match between two men who share the same surname (or a variant) means it is possible but unlikely that they share a common ancestor within the genealogical time frame. If you test additional individuals, you may find the person whose DNA results falls in between the persons that are eight or nine apart demonstrating relatedness within this family cluster or haplotype. It is most likely that they did not match 24-25/25 or 35-37/37 in previous Y-DNA tests. If several or many generations have passed, it is possible that they are related through other family members. The only way to confirm or deny the relationship is to test additional family lines and find where the mutation took place. By testing additional family members, you may find the person in between. This ‘in betweener’ is essential. Without him, only the distant possibility of a match exists.
10 or 11 Not Related A 56/67 or 57/67 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.
>11 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.