..how much do u intefere?dc are 3 and 1.3 and 3yr old has just started finding the joy in winding up her little brother. Pulling hair,pushing over,snatching toys etc.at the moment i get involved every time she does something...is this the right approach to be having or is this teaching a)her that fighting gets attention and b)him not to stand up for himself?he is big enough to hit back when he wants...
Kids (esp boys) need and crave "rough and tumble" play. So I think zero tolerance actually isn't a good thing. But you can set boundaries on what's acceptable. For example, rough-housing when one person isn't participating or enjoying it.
One trick to avoid rewarding the bad behaviour with your attention is to always give the wronged party the attention. So, "oh, poor ds!! DD hit you and that hurt!! DD isn't allowed to hit you!" rather than "DD, DON'T HIT DS!, that's not okay! naughty girl"
Your kids are still young but I've found the advice in Siblings Without Rivalry (a book by the authors of How to Talk so Kids Will Listen) to be invaluable as my kids have grown up. Their advice really takes the heat out of pretty much all their natural sibling fighting. Both have become good little negotiators.