I used to look after my two nieces whilst my sister worked and thez were a NIGHTMARE! My sister was never very strict with them at all. It even got to the stage were they would start being destructive,the 3 year old even drew on my white sofa with red pen!!! I found the best way to deal with this was to get the both of them into a strict routine and show the boundries. With the help of my sister we set out a few rules. We found that cutting out sugar really helped. We also got him involved in helping out around the house and teaching him how to do things himself. Just small things like picking up his toys and so on. I'm not sure if you already have a strict routine set out for him but if not I would advice you to get on into action asap. It's a tough battle but is worth it in the end. Just think in there. I hope this helps and wish you the best of luck. Kellie :)