At this stage, your kiddo is quite sensible and can understand words and actions in a better way. They are going to school and interact with children of their age. With a lot of influences coming their way, it is not unlikely that they develop a defiant nature at this point.
What you need to know
The rebellious nature can be due to a lot of reasons that the child develops a character that is not correct for his social as well as personal standing. You as a mother need to check his ways so that he doesn’t harm others with his behaviour. Kids defy the words of their parents and elders which is not a good thing. You as a parent need to sit with the kid to understand his reason for discomfort.
What you need to do
If the child is not willing to share then you have to take strict actions. If the child defies your order then you can take away his basic privileges like toys, candies, games etc in order to make his understand his fault. Make sure your expressions are effective enough to make the kid realise his mistake at once. This behaviour needs to be corrected or else the kid might transform into a negative character.