My first born twin was notorious for doing those sorts of things. I would take away whatever they were fighting over, sit her down in her chair and have a talk about how to treat others. I would keep them separate for a few minutes as well. They are now 3, and they are still jealous of one another. Sometimes, they would fight it out before I knew what was happening.
Just to give you some hope. I spoke with their daycare teacher last week. She asked me if they were sweet and loving with one another at home. I laughed and assured her they were more like Ali and Foreman. Apparently, they NEVER fight at school- only at home. They put forth a united front at daycare. The joys of twinsies!