In order to keep the focus off the narcissistic abusive person, they will blame shift on to you. This is a great way for them to avoid taking responsibility for their abusive behavior and induce you to question yourself. The best way you can prevent yourself from falling victim to their "tricks" is to psycho educate yourself about this narcissistic system as a terrible system gone wrong that affects families multi-generational and across cultures. Sibling rivalry is an unfortunate common fallout of this system gone wrong.