If the 'Guardian' has an obvious conflict of interest and can provide no documentary evidence backing his claims, THAN YES... I WANT THE COURT WRENCHING CONTROL away from him and putting somebody else in charge!
The court has all the information. In fact, I bet they have a little bit more information than you do. And they have determined there is no reason to sever his guardianship. Just because you have these people crawling aout of the woodwork making outrageous claims doesn't meant they are credible. Have her parents petitioned to have him removed for cause? Have they ever made allegations against him?