If I have POA for my brother who is 72 with Parkinson’s and some dementia,can I be sued by a non licensed caregiver iinjured helping him in his home

Yes, as the attorney-in-fact for your brother, you can be sued by a caregiver, even if unlicensed, who is injured on the job.  Treat everyone as an employee with payroll withholding.  You can get worker's compensation insurance to protect yourself and your brother from caregivers being injured on the job.  You can also discuss with his homeowner's insurance if there is any liability coverage included.  If your brother qualifies for SSI or Medi-Cal, he may also get IHSS to pay for caregivers.