Is a quit claim deed valid if the grantors, POA quit claim for her to a different relative?

is a quit claim deed valid if the grantors, poa quit claim for her to a different relative?...can a poa that does not have his name on a deed or title, do a quick claim to another party? the title would still be in my deceased grandmothers name (right before she died-alzheimers)my dad made him self poa and then quit claim to my youngest brother. my dad also passed away, what rights do the other siblings, to the brother that has the deed, have to any proceeds.. if it is not considered valid, then what?