I think arming yourself with information about ADHD is your best bet to break any cycles related. Get diagnosed, get them diagnosed, seek counseling if it's feasible. There are a ton of coping skills that can help, but they have to be learned, and counseling will help in that tremendously. If that's not available, there's a ton of resources online.

It's also important to know that ADHD isn't necessarily something wrong with you, it's an adaptation. People with ADHD tend to be incredibly well performing when they're in the right environments, which is the kind of thing that can be learned through counseling or research.