To stop such an order you would need to file the appropriate motion with the court that issued the visitation order. I strongly recommend that you seek counsel with a local attorney. These are not easy matters to handle. You will want to discuss what evidence and information you have to present. You will also want to discuss how and if you can obtain any professional third party input. Based on the age of the child, is counseling appropriate. If so, often counseling can help solve the matter. A report from the counselor may also be beneficial in any action to terminate the grandparent visitation.
Please seek an immediate consultation with counsel and determine how to proceed. Your son evidently needs some help in dealing with this matter.
In addition to Attorney Helfrich's insightful comments, I write to warn that the grandparents or you might ask the court to appint a GAL. This may add additional cost to the litigation, but be of benefit if there really is emotional manipulation at play.
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