I think there's a wisdom in aspects of religion; such as the insight that envy and jelaousy are 'deadly' sins. I have sibligs who have behaved like your freind - and it's relted to their suffering turning into resentment and hate. We may not be the cuase but I was not suffering, and they couldnt stand that. ther is a German expression which captures he sentiment, of rejoining inthe pain of another, so tht is what they want to inflict. I feel mostly sorry tht they have dropped soooo low !