Help needed for a 2year old ds

[jofeb04]

My ds is 2.3years old, and generally he is pritty well behaved.
However, recently he will not leave my dd (8months) alone, trying to stand on her, throws his cup at her etc.
Normally hes good with her, trying to make her laugh etc, and im not sure whats causing this behaviour.
Any help is needed, as its starting to get to me telling him to get off her.
Thanks

i have a 3yo and a 3 month old and 70% of time he is great with baby but 30 % he hits him, lies on top of him. We have tried naughty step, chart, and yes we have smacked when he has hit babe hard. It is in my mind jealouy and also you son is getting to the age that Mummy is everyting to him and will not like anyone or thing take you away. I now spend a bit of the day just with ds1 so he feels needed by me. Its not easy and i sometimes loss the plot and all my good intentions with ds1 go out the window. hth