Yeah I have the same thing with my older 2.. they are just about exactly 4 years apart. I have to say that since they are older it has gotten much better. What I had to do was make rules and make those rules known when we would go out. If either would break those rules they would be punished. However if they did get along and not constantly bicker they would get a little surprise at the end. It wasn't anything big, but they would see that when they were getting along mommy would do something special for them. Worked like a charm. Now I don't even get invovled when they are arguing unless they are being loud. But I let them figure it out for themselves.. they are older now though 8&12. So they need to learn to settle their differences themselves. I just need to get a pair of earplugs soon.