Children are often jealous of their siblings. There are ways to help minimize jealousy. Here are some that may be helpful.
Teach children that they are part of a loving unit. No one is more special than the next. When celebrating one child’s milestone, for example a young child’s achievement, have the whole family get rewarded. This promotes group pride and all benefit. (young child stayed dry, or in their own bed) all the kids get something.
Children are so open about their feelings. They are expressive and filled with wonder and discovery. They communicate with facial expressions, their vocalizations, and their bodies.
All children argue over many things. The degree to which they do this is reinforced by parental actions. What is it you do immediately proceeding and following the incident? Do you encourage discussion or workable solutions to problems which arise? Children learn to get along in the world better if they have siblings or friends with whom they can test their power. As long as limits are set and within reason. This is for you as a parent to decide. If your children are quarreling, there are certain ways to diminish this, but there is no way it can be completely eliminated.
One solution may be to encourage discussion and compromise. If this does not work a "time-out" may be in order. First, give a warning, i.e., " if you and your brother cannot work out a solution, I will try to help you find one. If there is no workable solution, on which you agree, then there will be a five minute "time-out" for both of you. Have them separate and spend time alone. If when they resume playing and quarreling begins again, a second "time-out" should be utilized. Behavior will not change overnight, but if you are patient, children will better learn how to get along.
When the children get along and resolve solutions on their own, reward them with praise and attention. "I am so proud that you were able to play so well together this afternoon and get along so well. That must feel great."
Be patient and consistent. Use warnings and limit setting to help children understand the consequences of their actions. Warnings are important. They allow the child to become more self-aware of their own behavior. Rules help the child to feel secure. Children need to know what the rules are and parents need to be consistent. If a rule is broken, consequences must follow (time-out).