As the children grow, the younger child may resent the older child because they do not get to do all the same things. Children may also have rivalries over possessions. If you want your children to share their things, make sure both children have to share. Personalities can be different, so not all siblings will enjoy each other's company. Do not try to force your children to play together because this can increase resentment.
Children often believe that their parents favor the other child.
Even if this is not true, your actions may be saying that it is. Comparing your children will only make the problem worse. For more information on sibling rivalry, talk with a medical professional. This information is not a tool for self-diagnosis or a substitute for professional care.