It is understandable that many parents who had repeatedly troubling or traumatic interpersonal experiences during their formative years - e.g. because of being bullied, ignored, manipulated, considered to be a disappointment, emotionally abused or abandoned - will continue to be affected by these experiences later in life. For example, they may continue to be easily triggered emotionally, with strong feelings of anger, guilt, shame, disgust or anxiety, and to re-experience ideas about disempowerment or of being unloved and insignificant. Emotional conditioning may have occurred to bring this about and to cause difficulties with thinking clearly and with maintaining stable and healthy relationships.
Good therapy, however, would be much more beneficial for many people in this position than cutting off their parents or parents-in-law. Good therapy, for example, might consist of researching, re-evaluating and reprocessing the past in relatively safe, calm and predictable or controllable ways, being helped to reframe the meaning of some aspects of what is remembered so that they may come to be perceived as being less threatening and relevant in the present day, looking at how to improve one's resourcefulness and generally expanding personal tolerance for the downs as well as ups of multigenerational family life.