A short "Durable Power of Attorney" (for health care decisions) can be signed (or affirmed vocally, or by gesture) in the presence of any witnesses needed, and then stamped by a Notary Public, legally making the person named on the document your immediate DPOA, and revoking any prior DPOA ... as long as you are deemed of "sound mind". I believe it is nearly as easy to switch General Power of Attorney (everything; finances, business, etc). As long as you are deemed of sound mind, and able to communicate, you can change these easily, and at will.
However, if your family member is not deemed of sound mind, or cannot communicate, then it won't be as easy. You will want a Lawyer, proof of the current DPA not fulfilling their duties, or testimony of qualified others to that effect. Contact a Lawyer through State legal services, or a Lawyer you trust and who will help you so you get it done right. So, the answer is yes ... absolutey!