I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today.
Unfortunately, harm is not required to be proved in order to get a conviction for gross negligence. Gross negligence is generally defined as a conscious and voluntary disregard of the necessity to use reasonable care, which disregard is likely to cause foreseeable grave injury or harm to persons, property, or both.
So, while your brother was extremely lucky that your nephew was not seriously injured, he may still be charged with gross negligence.
Under the law he could also be child with child endangerment---a much more serious violation that could lead to his children being removed from his home.
I understand that you may be disappointed by the Answer you received, as it was not particularly favorable to your situation. Had I been able to provide an Answer which might have given you a successful legal outcome, it would have been my pleasure to do so.
If you have additional questions, you may of course reply back to me and I will be happy to continue to assist you further until your questions have been answered to your satisfaction.
Would you please take a moment to positively rate my service to you based on the understanding of the law I provided by clicking on the rating stars---three stars or more. It is that easy. That is the way I am compensated for having helped you.
Thank you in advance. I wish you the best in your future,