|This is a normal part of development for your child. He may begin to play around other children, but it will be 'parallel play.' Children at this age are very self-centered and may play alongside each other, but it will be some time before they actually start playing together. Your child will probably not want to share his things and he may be very possessive, even getting to the point of getting angry and hitting if another child touches his things.
It is important to closely supervise children that are playing together at this age and reassure them that the other child will not keep his toys. Let him know that it is okay if the other child touches or looks at his things and that he will return them. Keep a few of his favorite items separate and not available for sharing so that he feels he has some control over things.
If this behavior problem does not improve as your child becomes more mature, then more treatment may be required to fix the problem.