Parental alienation syndrome describes a pattern in which one parent systematically undermines a child's relationship with the other parent — through criticism, manipulation, interference with contact, or cultivating the child's fear or rejection of the other parent — to the point where the child begins to reject that parent without legitimate justification.

Triangulation is a manipulation tactic in which a narcissist introduces a third party — a person, a group, or even an implied comparison — into a two-person dynamic in order to create jealousy, insecurity, competition, or a sense that your position in the relationship is conditional and must be earned.