Possessive case with who(m)ever in an object noun phrase

Question

Disclaimer

The question put forward as the pretext for mine's closure does not answer my question at all—that question contains “who(m)ever” in a clause acting as an object, which I have no trouble with. My question deals with a possessive contained inside a noun phrase, which is much more complex. Therefore, I request that my question remain open.

Question

Parents should use who(m)ever's last name is shorter on the form.

Should whoever or whomever be used in the above sentence? The way I see it, “who(m)ever's last name is shorter” is a noun phrase (NP) acting as the object of the verb use, while “who(m)ever's” is seemingly acting as the head of this NP^[1] (more specifically, as a possessive determiner formed from a relative pronoun—how the relative clause looks like, I'm failing to figure out—and the clitic 's, with another clause after that to modify the head?).

So, how should it conform to the sentence?

Should “whoever's” be used here? The following sentence makes perfect sense to me:

Whoever's (whosever) last name is shorter should be used on the form.

since “whoever” is acting as the head of the NP which is the subject of the sentence. However, here, “whomever” is acting as the head of a NP which is the object of the sentence, which throws me off and makes an argument for “whomever” appear more compelling in my mind:

Whoever's last name is shorter [...], parents should use it.

since the NP is replacing the object it, and the pronoun should be an object pronoun.

Is my grammatical analysis correct? Is there a general rule of thumb to use when encountering sentences like these? I am not a grammarist of any kind, so I'd prefer it if you kept your answers in simple terms! I greatly appreciate any and all of your thoughts on this matter!

Notes

1. According to the determiner phrase (DP) hypothesis/analysis, also used as an answer in this English Stack Exchange question. I'm using “head of the NP” instead of “head of the DP” for consistency and to avoid confusion.

Answer 1

Whomever’s is never viable — not as a possessive, not as a contraction, not anywhere. That leaves whosever and whoever’s as possibilities (see Later at end for more on that).

You have already learned this:

A dependent clause headed up by whoever or whomever is not affected by the role it plays in the sentence — subject, object . . . it doesn’t matter. The clause must be grammatically true unto itself.

Compare the clauses whoever likes him (where whoever is the subject of likes) and whomever he likes (where whomever is the object of likes). And then compare these sentences, all correct:

Whoever clause as subject: Whoever likes him gets candy.
Whoever clause as object: He gives candy to whoever likes him.
Whomever clause as subject: Whomever he likes gets candy.
Whomever clause as object: He gives candy to whomever he likes.

All that said, this hardly applies to your example. A possessive can never be a subject or an object; it’s a modifying interloper on its way to the subject or object. Its sole job is to serve its modificand.

Compare the clauses whosever cat likes him (where cat is the subject of likes) and whosever cat he likes (where cat is the object of likes). And then compare these sentences, all correct (if you can abide whosever — see Later at end):

Cat clause as subject: Whosever cat likes him gets chow.
Cat clause as object: He gives chow to whosever cat likes him.
Cat clause as subject: Whosever cat he likes gets chow.
Cat clause as object: He gives chow to whosever cat he likes.

No whomsever or whomever’s.

Later . . . whosever vs. whoever’s

Whosever is rare in usage. For most natural results, use whoever’s instead of whosever. Oxford English Dictionary (among others) straight up calls whosever “rare” and offers a scant two usage examples, ending at 1865:

whosever, pron.
rare.
The genitive of WHOEVER pron.: = WHOSESOEVER pron.
_{1739   ‘R. BULL’ tr. F. Dedekind Grobianus 133   Whos’ever Knife upon the Table lies.
1865   W. G. PALGRAVE Narr. Journey through Arabia II. 19   Whosever the footprint may be, the story is gospel among Mahometans.
Source: Oxford English Dictionary (login required)}

So:

Whoever’s cat likes him gets chow.
He gives chow to whoever’s cat likes him.
Whoever’s cat he likes gets chow.
He gives chow to whoever’s cat he likes.

Whoever’s all around.

_{Further reading: Garner’s Usage Tip of the Day: whoever; whomever.}

 

Answer 2

Somehow you are overthinking this terribly and coming to a nonsensical conclusion. You ask us to choose between incorrect assumptions.

Parents should use who(m)ever's last name is shorter on the form.

Should whoever or whomever be used in the above sentence?

No, they should not. You've got it all wrong.

Just as the possessive form of he is his not ❌ he’s, the possessive form of who is whose not who’s.

And there is no possessive form of whom: it is already the object form. If you need a possessive, you go back to the correct possessive, which I repeat is whose. For the same reason that there is no such word as ❌ him’s, there is no such word as ❌ whom’s!

Whose name is shorter? His name is shorter. Not who's name is shorter, not he's name is shorter, not him's name is shorter. And it doesn't matter one weaselly whit whether his name is the subject or the object. None. Don't touch it. It simply doesn't matter whether you need to use that noun phrase as a subject or as an object. Your possessive determiner does not change to him's or whom's or whomseverses's or any other crazy thing.

Do this and don't look back:

1. Whosever name is shorter wins.
2. Use whosever name is shorter.

Or colloquially:

1. Whoever's name is shorter wins.
2. Use whoever's name is shorter.

After all, you don't say "Use him's name". So don't try to do those other weird things either.

Answer 3

Parents should use who(m)ever's last name is shorter on the form.

who(m)ever's = the person whose

Parents should use the person whose last name is shorter on the form.

Can we use a person on a form?

Whoever's horse wins will get the prize.

Does a person get the prize or their horse?

He whose horse wins will get the prize

We give the prize to him whose horse wins.

He whose own life is without intrinsic value can not recognize intrinsic value in another. (Joseph A. Leighton; 1937)

"The Relation of Literature to Life" will not appeal to him whose main object in reading is amusement. (Warner, Charles Dudley; 1896)

Would the two above make sense with Whoever's and whomever's respectively? Would it improve them?

I don't believe these questions have a correct answer, but do think that, whenever there is any doubt at all, whoever's is preferable given a binary choice since anything with whom feels a bit formal, dated even, and can be replaced by who without anyone batting too large an eyelash.

Further, while the genitive form whoever's can be found in HANSARD (British Parliament Corpus) and COHA (Corpus of Historical American English), whomever's has only a single hit in COHA and no representation at all in HANSARD, and then the single hit in COHA isn't the genitive form but a clitic.