Have pity and feel sorry for the alienating parent.
I speak from experience, you do not have to be a psychologist or social worker to work it out. The alienator – (be them a parent, sibling or grandparent) obviously has severe insecurity issues and much emotional baggage.
By alienating a child from people or relatives around them, they feel they are securing their own love from that child – by process of elimination!! If they are the only remaining person in that childs/adult childs life the only option for that child (adult child) is to love that remaining person in their life – it’s not rocket science!!! By putting themselves first and depriving the child (children) of loving relatives they are instilling a behavioural habit into that child/adult child for later years. That child, or those children in multiple cases, will grow up thinking it is perfectly normal behaviour to alienate people from their lives and will teach their own children the same. Then history goes on and on repeating itself because no one has had the courage or foresight to put that child (those children) first in their life, and do the decent thing and allow that child (those children) to be loved by everyone!!!
I know to suggest pity and sorrow for these types of people sounds like madness, but their lives must be so emotionally disturbed and empty to put their own feelings first, they must feel so much bitterness and anger about something from their past
Maybe we should be trying to help them seek counselling or medical help, not blame them!!!