I had a friend since last12 year last year he told to me if you like you can Mary his sister the whole family is narcisist member now i came to know and now he know i know all is they will revenge or?

It's understandable to feel concerned about potential backlash from your friend's family, especially if you've identified troubling behaviors. If you believe they might retaliate, it’s important to prioritize your safety and well-being. Consider distancing yourself from the situation and maintaining boundaries. Surround yourself with supportive friends who understand your concerns and can offer guidance.