Interpretation of results

[KenG]

Thank you for providing this site and making so much information available. I have looked on the site and its FAQ and not been able to answer some questions I have. I hope you can help. I would like to determine whether three different families with the same surname are related. I have lineage for all three families from current generation to five or six generations back; then the paper trail stops for these three lines. Can yDNA testing determine at which generation [7th, 8th, 9th, etc?] any of the three lines are related [if they are]? How many DNA samples from each line would be needed to determine relationship? Within each line, there are some branches that do not have living male representatives. I know that yDNA testing cannot be done with the female representatives. Is there another kind of testing that can be performed with female descendants that can still be used in conjunction with male descendants to determine genetic relationship? Thanks.