my mother has custody of my son he is 5 long story there but he lives and has lived with me and my wife for 7 months we reciantally found out he has been exposed to sexual abuse somewhere and we have him in to see a therapist the therapist suggests we not let him have unsupurvised visits with his grandmother who has legal custody of him for various reasons and now she is threataning to take him back into her custody what can i do