Establish and enforce a limited number of developmentally appropriate rules . Your nephew must learn that behavior has consequences. Removal of a privilege is often an effective consequence. Chart his behavior. Record the times of his outbursts and what triggers them.
Children misbehave more often when they are tired or hungry.
Adjust the snack schedule or naptime to reflect his needs. Vary each day's activities. Make playthings available on a rotating basis. Balance quiet and active play options. Provide indoor and outdoor activities every day, even if your outdoor activity is only a brisk walk.