I have 4 children that do the same thing! It may seem strange, but I find them something they can do thats fun together and include myself. We play twister, or a board game.. but you have to be right there with them. I think that alot of times someone wants to be the "boss", so this also teachs them to take turns. If they still want to fight, its to there bedrooms. No T.v., nothing. Then they have to hug, and make up. I've even made them tell each other 3 things they like about the other person.. I hope this helps!