My parents are fighting (cross-families)?

Let them work out their own problems. Don't be worrying about what might happen. When the time comes for you to graduate or get married send the invitations to both parents and their spouses. If you mom is not remarried then it should include"guest". If anyone says anything then inform them that you do not want to exclude anyone and you expect all to act like mature adults. If one or the other wants you to take sides in an argument just stop them and say you do not want to be in the middle and they should work it out. Then step away. You will be happier and they will know that you will not be millipitated (sp)