What strikes me about your initial post is that you seem to be taking things so seriously or have expectations that your cousins are going to be similar to you in terms of musical tastes and political beliefs. I don't know why you would let things like that dictate how you feel about the relationship in total. Sure, there are times when I try to avoid political discussions with certain people, but I don't let differences of opinion determine my total view of the person or the relationship. We are all going to have to deal with things in life that are not exactly to our liking, but I feel that it's very wise to pick your battles carefully. As long as your cousin is not being rude to you either in person or online, I see nothing to be upset about if they posted things you disagree with about a politician. Life is too short to let such things determine your emotions or relationships. Let people be who they want to be and have the views they want to have.