Family overrode my POA by getting a new one signed in front of an attorney by incapacitated adult. What can I do?

I have been caregiving for my MIL and my BIL for nearly 10 years, I had plans in place when MIL passed to care for BIL. But in the 3 weeks prior to MIL passing, a family member felt they should pull my POA and accused me of theft of funds from them and got an attorney to void my POA and signed a new one with the incapacitated BIL to the family member who has ulterior motives (to take funds from banking accounts, own the home and RV's of BIL) After investigation from DHS Elder care I was relieved of all charges they were deemed unfounded. But how do I get POA back on my BIL? he needs someone to protect him from this family member.
The Dr. indicated prior to the date the new POA was drawn up that BIL was not able to make his own decisions and should not be doing this at all, yet they still did it? I so want to fix this so I can watch over my sweet BIL like I promised his Mom I would.
Family has not been in the picture for the ENTIRE time I have cared for them both, and now that they know he is vulnerable they pounce, and it is not right.
I so need help!