Power of Attorney, General vs.

Power of Attorney, General vs. Medical
My Brother has General Power of Attorney over our Mother, who currently resides in an assisted living facility. I would like to assume her medical care, since my expertise is in the medical field, and I do not feel he is qualified to make good decisions, and he has not proven responsibility in this area. Is it feasible for us each to acquire two different types of POA? If I obtain Medical POA, will his General (or Durable) POA supersede the Medical POA?

(Gen power of Att.

(Gen power of Att.) change will to living trust
I have General Power of Attorney for my older sister who is now completely mentally and physically incapacitated. With this legal standing can I create a new will or living trust for her? I want to name her 21 year old daughter as her sole beneficiary of her life insurance policy. (Her present will names her ex-husband.)