So, if one will is good, are multiple wills better? Short answer: nope.
What happens when a decedent has more than one will? Well, I can't speak to the laws in Michigan, where Aretha lived, but let's say she'd lived in Texas. Here's how this issue, called will construction, would be handled in the Lone Star State.
It's worth noting that in Aretha Franklin's case, and in many will construction cases, the purported wills at issue are written by lay people, not attorneys. A properly attorney-drafted will should avoid the issues noted below.
Is any of the documents a valid will?
First, we'd need to review the documents to determine which, if any, show "testamentary intent"--that is, purport to dispose of some or all of the person's property after death. A signed note saying "I give my house to Joe when I die" would probably be construed as a testamentary instrument, while "I want to give my house to Joe" might not be, since it expresses a wish rather than actually making a gift, and doesn't state that such gift is to happen at death.
Second, we'd have to determine if the document met the legal requirements for a valid will. A typed will is valid if properly attested by two witnesses, and an attorney-drafted will prepared by a knowledgeable estate planning attorney should satisfy this requirement. A handwritten, or holographic, will can also be valid even if not witnessed if it's written entirely in the testator's handwriting (testator=person making the will).
So, if the Queen of Soul wrote out her wishes for property disposition at death in a spiral notebook, as the article suggests, that writing could satisfy the requirements for a valid holographic will as long as she signed her name somewhere on the document and a witness can confirm that the handwriting is Aretha's. (So yes, if you found yourself on a plane going down and didn't have a will, you could write your will on a cocktail napkin.)
But if instead of handwriting those wishes she typed them up on her computer, printed the document out, and signed it without witnesses, it's not a valid holographic will, it's just her autograph on a piece of paper (I mean, it's still Aretha Franklin's autograph, so it's not nothing, but it's not a will.). What if she splits the difference, typing up her wishes, signing it, then going back and adding handwritten notes? Well, we disregard the typed portion and if what's left can stand as a will, it's a will.
Which documents comprise the testator's will?
Next, once you've figured out which documents, if any, meet these requirements, you'd have to consider their relation to each other. If the most recent document expressly revokes all prior wills (as virtually any attorney-drafted will does, unless, for example, there is another will in a foreign jurisdiction the new will is intended to work alongside), that document alone comprises the testator's last will. Otherwise, to the extent that a later document is inconsistent with an earlier one, the doctrine of "implied revocation" comes into play and the later provisions supersede the earlier ones. But to the extent they aren't contradictory, the documents should be harmonized and given effect.
So for example, if Aretha's first will gives everything to Kid A and a later will gives everything to Kid B, the later will impliedly revokes the first one as they are so inconsistent that they can't coexist. But if the second will just gives the car to Kid B, we'd harmonize the two to say that under the combined will, Kid B gets the car, Kid A gets everything else.
Beyond that, once we've figured which document(s) comprise the testator's will, the next step is to review and determine if any ambiguity exists, such as a property description that leaves the reader unclear which property is being given. In cases of ambiguity, Courts apply a series of presumptions to determine if the ambiguity can be resolved. If not, they can consider extrinsic evidence—evidence beyond the four corners of the will itself—to try to determine the will’s meaning. Without knowing more about Aretha's documents we don't know if this will be an issue, but it wouldn’t surprise me. She was a brilliant musician, after all, but not an attorney. As I like to say, clients think of will provisions in terms of specific items and specific people, while attorneys like to draft in terms of classes of property and classes of people for greater flexibility, where possible.
Stories about celebrity estate planning gone wrong make noteworthy examples, but issues like this are not uncommon with layperson-drafted documents. I once had a probate client come in for our first meeting with an attorney-drafted will that had the i's dotted and t's crossed. So far, so good, looks like a straightforward case. Then the client reaches into a file folder, pulls out a piece of legal paper with writing, and says "and we found this in a legal pad in her living room, does it mean anything?" The paper, dated after the other will, purported to be a will too. Suddenly, not so straightforward.
Was this handwritten document a will that stood on its own, should the two documents be harmonized into a whole will, or did I have an attorney-drafted will and a page of handwritten notes that fell short of a testamentary instrument? Fortunately in that case it was a moot point because all family members agreed on the same course of action, but had the documents resulted in different distributions, we may have been looking at a contest between the party who fared better under the handwritten item and the party who fared better under the attorney-drafted will.
And while Aretha’s estate is big enough that even after legal fees the distributees will get a lot, when issues like this affect everyday people, it can eat into a small estate. Had the testator in my case picked up the phone to schedule a meeting with her attorney to make a new will instead of picking up a legal pad and a pen and attempting to write her own, she'd have saved her family some time, effort, and money—a result she’d likely have preferred.