Your uncle should retain an experienced Pennsylvania estate lawyer to:
a) consult with him on whether this action makes sense given his circumstances;
(b), if so, the proper procedure for accomplishing such a transfer in that state; and
(c) have the necessary document properly prepared and executed.
Here in Connecticut, a beneficiary may do this through an "Assignment" and the Assignment may be executed prior to the estate's closing. Good luck to you and your uncle.
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I agree with Mr. Pankowski's answer and analysis. You could not use a disclaimer in this case, because then the uncle's share would pass not only to your aunt, but to other beneficiaries, as well. This would seem to defeat the intended purpose.
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