Jealousy in children is natural. However, in extreme manifestation, it can be a sign that the parent has not found the balance between showing feelings and distributing attention equally among their children. It can happen when parents have not found the balance between professional and personal life. Children with lower self-esteem tend to be more jealous, i.e. those who have not received enough unconditional love, acceptance and praise from parents.
Parents often shift their focus from the first to the second child, without realizing what a test this can be for the older child. They feel abandoned, less significant, and uncertain. They can become introverted, and negative towards the new member of the family.
The best and easiest way to avoid painful jealousy in the older child is to involve them as much as possible in caring for the younger brother or sister, at the same time paying special and showing appreciation to them for their help.