In general, children aren’t expected to share at such a tender age as sharing should be developed inside them through parents’ guidance/examples and their own understanding. Once they start to understand the importance of sharing and what ownership is, it would be easier for them to practice and get along with their playmates without any fights.
You should first encourage your child to have many playmates be it siblings, cousins, your friends’ children or neighbors. This would help them to socialize more and built their confidence while being able to practice sharing with them. Before any of their playmates come by, remind your child to keep all her/his favorite things and she/he doesn’t have to share them but any toys left out would be for everybody to play with.
Alternatively, you may try out by using responsibility chart. A responsibility chart should consist of task that your children need to complete weekly and use sharing as a start for the first week. A good task would be to let your children and their playmates decide how long each of them has possession on the toy instead of using an adult in the middle as the referee all the time. Remind them that if this doesn’t work out, the toy will be taken away and no one can use it. It’s a good incentive to practice being fair too.
Competitions are great ideas for your children and their playmates too! It doesn’t have to be a tough competition but simple ones involving their favorite hobbies or sports or interests will do the trick. Indirectly, they are also learning how to be cooperative and instilling the spirit of sportsmanship by accepting the results be it disappointments or proud achievements.
In any cases whereby your child starts to act up by arguing or fighting to get the toy, as parents, takes a strong stand. Don’t make your child apologize in front of everybody as this would embarrass your child but go together with them to apologize personally on behalf of your child. Sometimes, don’t rush to be the referee and overreact when your child take a toy away from a friend but let them sort it out themselves and most of the time they will continue playing without any fuss.
Never jump into conclusion that children are being selfish when they refuse to share but it’s because they don’t understand how to do so yet. It’s never an overnight issue for your children to learn sharing and being fair but its results will have your efforts worthwhile!