Scottish Continuing Power of Attorney

[Scottrain]

Grateful if someone could clarify the meaning of the words “ Whom Failing” from the following text which reads as follows -

i the name of granter.......living at address.....hereby appoint person A.......living at address.......Whom Failing, my nephew person B ....living at address ........

Does the Whom Failing only cover the death of the named Person A then Person B the nephew steps in as substitute attorney?

can anyone confirm please.