Powers conveyed in a power of attorney are often less powerful than many people assume. First be sure your brother truly has the legal obligation to act; most powers of
attorney take effect only when the principals"”the person for whom they are made"”lacks the legal capacity to act for themselves.
So if your parents need some help in their medical and daily living needs, but are still basically of sound minds, then it is most likely the power of attorney has not taken effect. While your brother's lack of attention is lamentable, there is nothing preventing you or other more head's up relatives, neighbors, and friends from pitching in where needed"”or from taking steps to secure help from outsiders if that seems more feasible.
And as an ounce of prevention: If your parents' are still of sound mind and so able to reconsider and change their choice of possible agent, you might want to consider broaching this subject with them. Truth is, many parents simply name the eldest child to act as the agent in a DPA, without giving more thought to who might be best suited to the task.
However, if your brother actually is legally empowered to act in the DPA"”either your parents are incapacitated or the document was written to take effect immediately"”but he is not doing his job, then you are in a different boat.
First, try to have a talk with him to find out why and how he is shirking his duties. You may be able to come up with easy solutions to fill in the gaps where needed.
If your brother is empowered, but plain uncooperative and neglectful, then your only option may be the somewhat drastic one of going to court and having him removed and replaced. For information about how to proceed with this locally, first consult the probate court nearest to where your parents live. Most such courts now have websites brimming with information that you can find by searching "probate" and the name of the city or county.