Obtaining a POA?

My grandmother is asking to go home. She has dementia. She is currently in a nursing home. I'm willing to take her home with me, but my uncles say no. The facility she is in is substandard and her children rarely visit. Only one of my uncles is on file at the nursing home. However, there is no official POA. Do I have a right as grandchild to get custody of my grandmother and take her out of the nursing home?