I am impressed by your courage and clarity in relation to such damaging patterns of interaction Mariene. You are right - it really does begin with parents' abuse which the offspring emulate in relation to the child that is being scapegoated by the so-called adults.
It's hard to understand how people develop that level of malice and sheer sadism, that they can enjoy hurting someone else.
I think in my siblings' case, all the females felt insecure, then 3 out of four of them had very acrimonious divorces and so out of their unhappiness, they targeted me who had refused marriage and stood against other patriarchal normalities in Muslim culture. Thank you for sharing your experience and hope you can write in more detail if you feel like it. Such people fear nothing more than their exposure; which empowers the rest of us to get wise to their various kinds of manipulations.