If the injury suffersed to your son thirty-nine (39) years ago was caused by your "ex" neither you nor your son have any claim against the "ex" due to any claim would be time barred by your state's statute of limitations. Rather your recourse for your son is to see about certain governmental benefits through disability and social security given his injury and physical condition.I suggest that you consult with an attorney that practices law in the area of governmental benefits for assistance.