Personality disorder. Strange behaviour.

This is all about my sister from another mother as everybody in his family looses their senses as her behaviours is like hippocrites. She believe on what she sees from her eyes, lack of perception, lack of logic, believe on friends with benefit( she is only good for that person who is benefited to them) , who is not benefited to them she feels like let them go to hell. This is not only her contion same implies on each family member of her family like brother, sister, mother and father. One more thing about them is that her father was reputed doctor so I feel like they got some personality disorder as narcisstic personality disorder as earlier they were very poor but after some time they earn lots of money. As this play important role in behavior change. If there is any cure for this personality disorder then kindly tell me how can I deal with them as they totally destroy my personality due to their behaviour as it hurt me so much when I see their strange behaviour.