I have 6 yo twin boys. They are driving me crazy. (I do have PMT and will have for another 2/3 days). They fight constantly. Can't seem to stop. Starts as playing with lots of laughter but inevitably gets out of control till one is in tears. They seem to need to do it . I can't bear it - it's like nails down a blackboard. Have banned them from doing it in same room as me but still it goes on. Someone please explain to me why they do it and how I can deal with it.