Some schools will extend courtesy interviews to immediate relatives of faculty/students/graduates, assuming the applicant is relatively competitive. I have a close friend who interviewed at one of the Manhattan titans last cycle as a 3.5/507 ORM with no research. Her father is the chair of a department at said institution and her brother goes there. Listing someone you barely know will have no impact on your app.
Eh depends on who is advocating for you, but yeah generally it doesn't matter. I can also see a scenario where if they want to accept you they might go to the person you listed and be like, "so we are considering accepting X, they said they knew you. Are they actually a serial killer in disguise?"