I feel that my brother, who is our mother's financial POA, has an interest in her finances. What can I do?

I CANNOT PROVE IT BUT EVERYTIME WE DISCUSS GETTING HELP FOR MY MOM, WHO HAS DEMENTIA, POST HEAD SURGERY & LIVING ALONE, HE ALWAYS DISAGREES. I HAVE MED POA FOR OUR MOM, & EVERSINCE SHE GOT OUT OF THE HOSPITAL 6 MTHS AGO, I HAVE BEEN TRYING TO TALK HIM INTO GETTING HER HELP PER HER DR'S WRITTEN ADVICE. HE KEPT SAYING MOM DOESN'T WANT & NEED HELP OR THERE'S NOT ENOUGH MONEY. SO I TOLD HIM TO SELL OR REVERSE MORTGAGE HER HOUSE. HE OPENLY TOLD ME THAT HE WANTS HER HOUSE. HE THEN SUGGESTED HE WOULD MOVE-IN & TAKE CARE OF HER INSTEAD. ITS A GOOD IDEA. HOWEVER I DON'T TRUST HIM TO DO A GOOD JOB. 1ST, HIS WORK & CONDO IS IN L.A. & SHE'S IN SAN FRANCISCO. HE MIGHT LEAVE HER ALONE TO GO TO L.A. 2ND, HE LIVE'S LIKE A PIG. HE CAN'T EVEN CLEAN HIS OWN CONDO. I LIVE FAR AWAY. IF HE NEGLECTS OR ABUSE HER, I WOULDN'T KNOW. SHOULD I LET HIM TAKE CARE OF HER ANYWAY SINCE MY MOM DOESN'T WANT ANY HELP? IM DESPERATE. I NEED SPECIFIC ANSWERS AS TO WHAT TO DO, WHO TO CONTACT (WITHOUT DESTROYING OUR RELATIONSHIPS) OR WHERE TO GO.