It becomes a case of vicarious living. This is where adult child work comes in handy through your journey. Need not be the oa aspect, as much as the dysfunction aspect.
Sometimes they the parent with narcissistic tendencies will attach a real or imagined pain to one or more of the children. If there's a blow to the ego, watch out, there's hades to be paid.
Acoa's oft overcompensate in future relationships. A pattern is formed.
One thing I learned, there's a near or full blown manipulation of the parent being uncompromising. Through anger or tears. Gets submission. Then future pattern leads to being walked all over, so to speak. Creates also inner conflict in parenting. Best to resolve before, soon during or asap[if parenting ]. Mine were in diapers when I zoomed through countless books, hours of therapy and as many meetings i could escape to.