I wonder though....
Grandma has been collecting welfare for the child. That means that the state of TN had to be looking for the father to collect child support to reimburse them for the aid the child was receiving. Therefore, legal dad's paternity might have been disestablished as part of that.
I think that the only possible danger is if that happened, and the state of TN has an open case. If dad's paternity were to get established now, the state might go after him for that aid.