Ever heard of a brother being DFD and just walking away from family support?
Playing the "parental alienation syndrome" card it possible, but it is definitely an uphill battle all the way. In the U.S. a judge can force shared and/or joint custody of minor children. But judges can do little or nothing to prevent a parent from alienating their children against another parent. Nothing.
If the alienating parent is successful, the children will absolutely shun the other parent as soon as they become of age.
The psychological means of manipulation employed are powerful, generally applied unconsciously (although cult members have learned them well) and not subject to any legal means of prevention, redress or judgement.Anyone wanting to really understand this should read Richard A. Gardner’s exhaustive book on the subject: The Parental Alienation Syndrome: A Guide for Mental Health and Legal Professionals.
It's a challenging read, but for those that undertake it, you will clearly understand the power of the psychological forces involved.
A relatively quick primer can be found here: Parental alienation syndrome
thanks for posting the info @jp1692 - I think I've read something on this forum about adding something to the divorce agreement that restricts attendance to all meetings or conventions and going door to door. I would definitely be looking into some sort of legal means of limiting the indoctrination. There must be such a sense of powerlessness for df'd parents who have to share custody.