My twin granddaughters are always arguing, competing and fighting with each other. They rarely do as asked making them totally uncooperative. This behaviour takes up so much time that as a grandparent I rarely experience any joy with them. It's getting to the point now where I spend most of my time shouting at them. Obviously this is not what I want to be doing and I'm exhausted with it all. I'm wondering if their behaviour is common twins behaviour?