Brother has a DPA for MOM. Mom has been put in nursing home and won't let his sisters call to see haw she s doing.

The agent under either a Durable Power of Attorney or a Medical Power of Attorney does not have the authority to make this decision.  Authority to share medical information is granted by someone (in this instance, your mother) by signing a HIPAA Medical Information Release stating who may disclose medical information, any limitations on what may be disclosed, and to whom it may be disclosed.  Sometimes this is a separate document.  Sometimes it is incorporated in the Medical Power of Attorney. Please keep in mind that nusring homes typically designate one family member as the point of contact.  This is designed to assure that one party has all the information and can share it with others rather than each person having a piece of the picture (recall the story of the blind men and the elephant).