Yesterday I left my brother's house in a rush. His daughter 11 has ADHD and I find it very difficult to control myself when she is mean and moderately violent to my DS aged 6. My brother and his wife seem to ignore what's going on and I just cannot understand this. I feel if she was my child I'd be much more vigilant and intervene more. I'm now feeling so so guilty. I know she can't help it but I can't shake the feeling that she can behave fine in friend's homes etc. Please help with some advice about how I deal with this. I know I'm getting it all wrong.