I suspect more is happening here than we are being told.
You have advice to speak with patient first before worrying about what another relative says.
You have advice that the medical power attorney may entitle you to view patient records depending on how the power of attorney is written. Without anyone seeing the actual power of attorney it is not reasonable to expect expert and definitive answers in this forum.
If the patient is able to make their own decisions, the doctor is right in that the medical power of attorney will not allow you to make medical decisions, but that is not what you said you wanted, you just want to know the medical condition. No decision making involved.
