New specimen question

[dennis]

Lane:
I assume you are talking about a Y chromosome test. It is considered best to sample the oldest living male with the surname. There is usually no difference, but there is always the chance that a rare mutation event occured between your dad and you. The fact that there was a cousin marriage has no effect on the Y chromosome. The important criteria is that both males have the same surname. Drugs and alcohol do not affect the test results.
Dennis WEST
WEST, GIBBONS, PARKER surname DNA projects.

I just got a kit that I had planned to get DNA from my Dad.
One of the descendants we want to test against is from a generation down. I could test my brother instead of Dad so the tests would be in the same generational timeframe, but my brother takes a lot of medication and drinks alcohol.

Also, the second guy descends from first cousins that married back in the 1880's.

Question: Is the "Y" chromosome affected by generational differences, drugs and alcohol, or intermarriage?
Should I look further for better test subjects??

thanks!