If your ex is alienating the children, there are steps you can take. Be aware that Parental Alienation
can be extremely difficult to counter if your ex is truly determined. Some of these articles may be of assistance:
Document the alienation as thoroughly as you can. If the alienation is severe, consider asking the court to intervene by ordering a custody or parenting evaluation. A trained evaluator should be able to discern the extent of the alienation taking place, and may be able to recommend to the court that custody be changed or reversed,or that sanctions be imposed on the alienating parent. Be aware that the courts may not recognize or take the alienation seriously, regardless of its severity or how well documented it is.