I reported an incorrect credit for my son but got declined. Need help and advice how to delete it.

After I claimed my son's page I realized there is an incorrect credit under my son's account. I think the credit belong to another adult actor who has the same name as my son. It was a short film that has gay romance, and my son was only 8 years old and didn't participate any part of the film. I submitted twice to ask IMDb to remove the credit but both times got declined and IMDb asked for proof. How can I provide proof when my son was not cast or in any part of the film? Can someone please help and guide me?