Two siblings, ages three and five are bickering over the toys. The parent admonishes the younger child, 'You are almost four, now share.' The older child next hits the younger child and the parent shouts, 'Don't hit' you have to love your little sister/brother.' The stage is set for the parent to develop a rivalry between the children with the toys viewed as a valuable and limited resource. What is sought though, is sibling harmony, not rivalry. 

Children go through developmental stages where at one stage they are almost incapable of sharing, to the next stage, when they finally develop an ability to share. In developmental terms these stages are described as parallel play and cooperative play. 

Parallel play is most common in two to three year olds. The main feature of parallel play is that the child tends to play alone, even though the child may be with other children. For instance, give a two to three year old a ball and they will happily roll it around by themselves but will likely be unable to enjoy rolling it back and forth with another child. 

Cooperative play comes around four years of age and is usually well developed in the five year old child. Give these children a ball and they can happily roll it between themselves and take turns using it. 

Thus pre-school siblings who are close in age may find themselves in conflict. When at play, the younger will have difficulty sharing and because of this the elder may become upset. The issue isn't love or rivalry though. The issue is one where each child is at a different developmental level. Placing the problem into a context of sibling rivalry only creates a problem where it doesn't have to exist. 

The solution is to explain to the older child that the younger hasn't yet learned to share. The older child can be commended for having learned to share and can also be commended for having patience with the younger sibling until the skill of sharing has been learned. Helping the elder sibling place the issue in developmental terms helps release bad feelings the older child may have been harboring. Their sibling is no longer seen as bad, just younger. Further, the older sibling can be encouraged to share their toys with their younger sibling to help teach or role model how to share. Now, instead of developing sibling rivalry, the parent encourages cooperation and understanding in the older sibling, thus helping to develop empathy and caring. 

As for the younger child, this child can be encouraged by the parent to share and take turns with the toys. Depending on the age of the younger child, it may be necessary for the parent to take the toy away and give it to the older child to have a turn. It is important that the parent take this action and not the older child. The parent has legitimate authority to make the decision whereas the older child does not. Further, in taking the toy from the younger, the parent should tell the child, 'Time to share' It's your brother's or sister's turn.' Thus, play or use of the toy is a parental decision and not something the younger child can hold against the older child. 

As both children grow and develop, both will achieve cooperative play. Because the parent will have encouraged empathy and cooperation in the older child, both may now come to share well between themselves without parental intervention. The children's relationship will remain intact. This is sibling harmony and the way to a lifelong mutually supportive sibling relationship. 

Assume your children love each other' Now just teach them how to get along. Understanding developmental differences is the first step towards sibling harmony.