hmm, I went on to have a DD, and DS1 and DD1 often play beautifully together ....
It is tough going. I think 'tiger cubs' when they fight. All animals scrap with their siblings, don't they? Unless blood is drawn they can get on with it - but it helps that they are very close in age.
I was about to suggest keeping them out all day - but then remembered that's what started all this!
anyway, we're on the countdown til term starts so peace is imminent
failing that, a glass of wine with lunch can be most beneficial