Sibling rivalry is the training ground for all other human relationships. Look at is as a positive. They are fighting for individuality and for first place with their parents. I don’t believe parents can accomplish peace by making everything equal. Develop each child’s individual interest and spend time alone with each one praising their accomplishments and special traits. They are really fighting for you, not each other. Nonetheless, using sibling fights to teach empathy and fairness will make them better human beings.