My sister executed a POA in 2010 (it was notarized and recorded as required in the state of California). In the POA, my sister (who has MS by the way) appointed her husband as her 'Agent', and another sister as the 'Successor Agent'. The 'Successor Agent' name and address (in 2010) is clearly stated in the POA.
It is not now 2017 and my sister's husband no longer wants to be the 'Agent' under the POA (he is unwell), and wants the 'Successor Agent' to act under the POA. The 'Successor Agent' is willing and able to take over the role as 'Agent'. Is there anything (e.g. document) that is required?
I should mention that the sister who executed the POA in 2010, and who has MS (multiple sclerosis) may not now be considered mentally competent to execute any documents.