Which kind of relations are considered incestous in Christianity?

My question, in strict propriety, is specifically what kind of relationships are defined as incestuous in Christianity? I am guessing that it is forbidden to marry one's parents/children or siblings but what about other relations like first cousins. I would appreciate some sort of a reference to maybe a specific passage in Christian holy scriptures. Is this something specifically commanded by God explicitly, listing forbidden relations? Or is it some sort of an interpretation done later by a scholar which is widely accepted today? And I am talking about Christianity in general encompassing all of its sects. Do different sects have different rules?