I'm having difficulty in getting my just two year old to do as he's told. Obviously my standards are low in what I expect of him as he's only two. The main issue is him hitting his sister. If he throws a toy I take it away, easy. But I can't take his sister away. If I tell him off he just smiles, if I make him sit on a step he just sits there smiling then goes straight back and hits her again. He's generally not to badly behaved but is inflexible and more physical compared to DD who has never hit back once and can be a bit of a push over. I don't want DD to think being hit is okay and something she has to put up with but nothing I do affects his behaviour. His language is very good for his age so he understands we don't want him to hit he just doesn't care.
Any suggestions?