If one thing is unrelated to another, there is no connection between them. You can also say that two things are unrelated.
My line of work is entirely unrelated to politics.
我的职业与政治完全无关。
If one person is unrelated to another, they are not members of the same family. You can also say that two people are unrelated.
Jimmy is adopted and thus unrelated to Beth by blood.
吉米是被收养的,因此和贝丝没有血缘关系。