Your father should meet with counsel that can clearly articulate the problems with this type of planning. The Will might not have any legal effect depending on your father's intent, but when dealing with intent then we are likely looking at a court proceeding to determine rightful beneficiaries. If his intention is to avoid probate he might consider a revocable trust as a way of ensuring a probate estate is not commenced on his death and his assets are properly distributed amongst all three...
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Unless this matter is supervised, once appointed there is little difference between a "formal proceeding" and an "informal appointment" (i.e. the requirements are the same). I recommend you chat with competent counsel to determine the necessity of any action. This "Answer" is not legal advice.
I am sorry to hear of your loss. You likely should file a Petition and Order for Assignment with the probate court to take title to these assets. There are rules that may forbid a creditor from being paid in a case like this and you should seek competent counsel to review this matter. This "Answer" could not be and is not legal advice.