I gave the following answer on another site:
The will is irrelevant with regards to the IRA.
The IRA beneficiary designation is what controls who inherits the IRA.
The IRA bypasses probate as it was no longer part of your grandfather's estate at the moment of his death. It automatically belonged to your uncle.
Your uncle is the beneficiary. He gets the IRA and he is subject to the IRA rules for inherited IRAs which he would be wise to read at:
https://www.irs.gov/pub/irs-pdf/p590b.pdf
Your uncle needs to be aware of and follow those rules lest he be hit with a whopping tax bill.
Of course, if he wants to take a large distribution, pay the tax on it, and give the money to you and your brother, he's welcome to do that. Though I doubt that he will be willing to do that once he learns that the money is all his and that giving any of it away will cost him plenty. But, hey, you know him better than I do.
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An attorney provided the following response to the question:
"Rather than getting a court order, your uncle likely can just submit a disclaimer to the institution holding the IRA. Assuming your grandfather was not married at the time of his death and that there were no other/alternate beneficiaries named on the IRA then the effect of the disclaimer would be that the IRA becomes an asset of your grandfather's estate and thus divided as his will specifies."
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Note from me:
The latter suggestion means that the IRA would have to be probated along with the rest of grandfather's estate.
