So is this treated as if who were an adjective, so it has to be conjugated for person and number?
I'm guessing, but I think "kimim" is not an adjective, but actually the predicate (although adjectives can apparently be "turned into a predicate" in the same way): "I who-am?"
Funny, in Polish we also use "kim " for "who" : "kim jestem" = who am I, "kim on jest" =who is he or "kim jesteś" = who are you
Actually, looking at that, it makes sense, I shall just confirm by asking the nearest Turk...
Is the ending -im necessary or could you also ask "Ben kim?" Or for a more common situation, would you need to say "Siz kimsiniz?" or would the shorter "Siz kim?" suffice?
In one sense it has a meaning, because it's a fairly common Korean name, haha. In Turkish, however, it's not grammatically correct... It's something like: "I who?"
Most of the time we use "kim" on it's own because we're asking about "him/her" (o) or "they" (onlar)... And 3rd person doesn't need a personal suffix. = O kim? Onlar kim? Baban kim? (Who is your father?); Öğretmenlerin kim? (Who are your teachers?)
But for "you", "I", and "we" personal suffixes are required to complete the sentence. --> Sen kimsin? Siz kimsiniz? Ben kimim? Biz kimiz?
whom asks after an object, but "to be" does not take an object in the objective case, it joins a subject to a predicate in the nominative case.
At least traditionally -- in the sort of grammar where you would use whom, you would also say it is I.
If you say it's me, then you probably wouldn't be using whom in the first place.