My brother has full POA (I believe) as he & my sister refuse any communication with me. Anything I can do?

My mom is now screaming things to me. I have been threatened by my brother with APS & told him I welcome APS, an arbitrator/mediator, geriatric specialist & even lie detector tests for myself as well as my brother, his wife & my sister. My 56 yr old brother us in very poor health, on disability & hus 47 yr old wife nor his 3 sons ages 20 to 27 have or do work/have a job. They have my Mom convinced of something so age wont even communicate with me. We were very close before Dad died 5 yrs ago & she allowed & believes my brother. I believe her mind is going with proof & they are taking full advantage of her finances & keeping me away. So sad & So wrong. Anything I can do?