If they are rivals, I don't think it can be helped. It'll just be the way they are.

As I said in another thread, my sis and I have always been rivals, our entire life. I am the weird, leftie, alternative hippy and she is the golden child with the sun shining out of her backside. It's just the way it's always been...our personalities are WAY too different, probably. We are 13 months apart and apparently, when she was born and I wa 13 months old, I pretty much had no interest in her, even then.

I am worried about having another girl and having them turn out like my sis and I, but as parents, our kid's personalities are something we probably have no control over.

I can't offer any advice as to HOW to try to establish a friendly relationship...when you find out how, please let me know! :-D