I'm always dismayed when I hear therapists advise people to cut ties with their parents, I'm surprised they don't suggest you ask your parents about their upbringing, just so you can get an insight into why they are the way they are. My sister is very nasty about my mum, but if I'm honest, my mum was better to us than my sister was to her daughter. I don't think cutting ties should be done unless its absolutely last resort.