Helping siblings. Fighting among siblings is a universal issue. Some key points that help: mom & dad need to be on same page & agree & not fight in front of kids ever; praise good behavior as much as 10:1 for every correction you give. Modeling words & touching/behavior you want them to follow helps. Supernanny has many great pearls for this as does Dr. Ray http://drray.com/bookstore. Family Enrichment in SF also!
Have conference. If the kids are old enough, sit down for a discussion.Do so at a quiet time.Explain that when they fight/disrupt the house etc.It makes you feel sad, angry, whatever.You have decided that is not acceptable & worthy of punishment.Decide as a group the punishment due for the various infractions, yelling, hitting, pushing etc.Post it on the fridge & enforce it.Consistant penalties allows for choice.