answer:I have an autistic almost 7-year-old grandnephew, and it can be very trying, even for those who love them the most. His voice is naturally high-pitched and often he needs to speak very loudly or shriek. Melt-downs are inexplicable and at random; in our family they are resolved only by his mom, dad or grandmother physically removing him and relocating him to an area that he knows is his quiet spot, where no one will bug him or take his toys. It is specially designed for him when he visits his grandmother. His 9 year old and 3 year old brothers can also trigger a tantrum, even when they are doing what they normally do together. At the moment, sadly, there are no answers. I love your good intentions but I would probably not let your daughter spend time with him. Does her son go to some sort of school or group and is he getting the support offered by social services? He should be getting daily behavioral therapy, occupational therapy, and physical therapy, and the mom should be provided both support and resources. Can you spend a little time with her without your little girl? LIfe for these parents is very difficult.