My mom and brothers are keeping me from seeing and speaking with my dad who has Alzheimer’s. What can I do?

I had DPOA, which my brothers revoked. They have convinced my mom that I am in a “bipolar state”, which is untrue and unfair. My dad had always taken care of everything but now there’s a huge imbalance in the family due to his illness. Up until a month ago I saw my parents 2-5 times a week, driving them to doctors appointments, spending time and taking my dad out to give mom a break. There was a family blowout and my brothers who previously didn’t get along, are now united in revoking the POA and taking my name off of bank accounts etc. it’s very complicated, I’m stepping back. My mom said she’d contact me when she’s ready. When I have called before she refused to let me speak to him. My dad and I have always shared a bond none of my brothers or mom have had. I miss my dad and hope the stress/drama hasn’t effected him to the point where he won’t remember me.