u/Few-Psychology-7712

Hello, so for a little backstory I'm just your average black guy that lives in Alabama. I was doing some research recently and discovered a pair of great grandparents with the last name Jackson. Both of whom are mixed and share the same last name jackson. Both of their father's name was Jesse Jackson which was even more confusing to me, but it was two different people, however I did even further research and discovered that my two great grandparents are 2nd cousins which upon even further digging leads to them sharing distant ancestors with Andrew Jackson. So I was wondering does this effect DNA and if some matches I have appear closer then they are, because those set of great grandparents are related? Or if it effects anything in general. I'm also curious if people being related in family trees effect DNA ethnicity results like causing them to be doubled.