Have you talked to him about why it's not nice to do that? What I would do is tell him that he cannot hit his sister for any reason because he is not the parent. If he's angered by her then he should come to you or daddy and you will handle the situation. If he doesn't then he goes to timeout a few times and if he's still at it yes you need to spank him and then not let him around the baby again. They know better and need to be stopped. If you see him getting frustrated with the baby then try telling him to do something else away from the baby and hopefully that will help.
at 5:26 PM on May. 12, 2010