How do I get help for my aunt and uncle that are mentally deteriorating and physically deteriorating?

Certainly there is help. Start by calling their county Office for the Aging. They can send out a social worker for them.

The first step is to visit them and talk to the aunt. Your aunt may well feel "trapped" with her brother as he gets a disability check and probably has title to the house. She probably has no income aside from the brother. Should he be put in a facility then she will be left with nothing. Someone should get POA for the brother and sell the house to generate money. The money can be used to rent a small adult apartment where some helps are available for the uncle. A relative should offer to take in the aunt for now. With less stress she will come to be able to care for herself.

Call their Adult Protective Services with your concerns, and you could contact their local police to make a welfare check. From that report, services can be provided if they are willing. My prayers with them.

I suggest a visit and family member become Health Care surrogate for aunt and alternative poa for uncle.
Assess aunts needs no mention re her age, possibly she needs to have assistance w application for soc sec disability or ssi.etc. Longterm care can be applied for for uncle through elder affairs even if not age eligible disability eligible since needs caregiver in home. If aunt just needs help this may solve need with aid or visiting nurse in home.
I suggest famy mem er to initiate alternative.
If placement is meeded the home may serve better as reverse mortgauge.
Or possibly gift to hospice for the two of them. In return for their care.