This kid really is annoying but my cousin wants support. AIBU to deny it?

[AxioCheese]

My cousin has a 9 yr old son. He's sweet but really annoying. Constantly jiggling up and down, interrupting conversations and trying to join in when he can't do whatever it is.
My cousin says he is being bullied at school because other kids won't play with him and say he is annoying.

Obviously I'm not there but it doesn't sound like bullying. Just that they are normal kids who want to play with their friends and not be interrupted all the time.

My cousin is upset because I won't take her 'side' in all this.

Should I pretend I don't notice the way he is and just give her moral support? My family think I should but it feels wrong. AIBU to stick to my guns?

Also in case it is relevant he's been assessed for ADHD and hasn't got a diagnosis.

Yes during class work/group work but at playtime kids should be free to play with who they want.

I don't think it's bullying either op and I have a child like that, now grown up. She is lovely, generous, loyal, kind, but she was also annoying, loud, whiney, pedantic, and other kids didn't much like her. They didn't dislike her, they just didn't want to play with her, and as she got older, didn't want to hang out with her. Was it upsetting yes, it was fucking devastating, it is nearly as hellish for the parent as it is for the child, but you can't make kids like another child or force them to play with them. I think you need to be sympathetic and supportive to your cousin and her son, without getting drawn in to the rights and wrongs of the situation.