Totally agree. There are so many comments saying, "address the behavior not the child", "talk to the mom", and "no need to be cruel." All of that is GREAT advice... for a NORMAL situation. This is not a normal situation.

There's no chance the grandparents, aunts and uncles have reached this level of disgust and distance without trying all normal avenues first - like when the kid was 3, 4, 5...9. This was clearly a last-ditch moment of desperation for OP on behalf of his entire family because this is now affecting every aspect of this kid's life. No amount of "when you do X I feel Y" was going to work here. That only works when a kid CARES how he makes people feel, and CARES how others feel about his behavior. Which this kid didn't. This kid needed a proverbial slap in the face, and that's what OP delivered.