Change of Custody

Hello,
My question is tricky. I am concerned Grandparent, children live in NC and visit non custodial in Ohio. Visitation has been ok for the most part, some issues. We have a 12 yr old boy and 10 1/2 girl. Without going into a long story I will give a short version. Grandson is miserable, has been for nearly 3 years, wanting to live with non custodial. He wants to talk to judge and has expressed this to custodial parent, who makes remarks back to him that aren’t right, instead of explaining the situation. Both have had past and recent councelling, Grandson expressed in sessions his desires. He states nobdoy will listen to him and why can’t he decide or talk to the Judge. What is upsetting now is that he’s having trouble in school with grades and attitude. With all this the non custodial has asked custodial parent just to let him try living here, will not allow. I am concerned about his emotional well being and this will forever mark him now and in his future. I have read that Judges will not split up kids, but with this going on, why not? The best interest should be the point, not a court best interest. Besides going into another long drawn out court battle, is there another way this could be done? Agencies or groups that represent children or interview them and do a letter of recommendation and forward to attorneys and parents? From there hopefully an agreement, even a temp, to see if he would do better with non custodial? Sorry this went on too long, just worried about another victim of divorce, who is my grandchild.
Thank You

Their parent needs to file a motion to modify and see what the judge will do.