It is you who are/is ...

"C'est moi", rather than "C'est je." The grammatical explanation is that
"moi" is used here disjunctively, as "ce" is the subject, so "je" is the complement rather than the subject. "Me" and "us" are the English disjunctive versions: "it's me", it's us". "It" is the impersonal subject, "me" and "us" the complements.
A bit more on this: the disjunctive is where there is no further verb attached to "moi" or "me", etc. When there is another clause: eg "It is me who is wrong"/"It is I who am wrong"/ "It is me who am wrong" "It is me who is" - "is" here governed by "who" which in turn may refer to either "It" or "I/me". In French where the persons of verb, and their tenses, are much more clear: "It is we who were wrong" would certainly be "C'est nous qui nous sommes trompes", and "nous" here is disjunctive, as proved by "moi" if it were "c'est moi qui me suis trompe". Now that is an argument for saying that "It's me who am...". But it doesn't sound right, does it?

Does 'who' refer to "it" or to "you"? It is, you are. You are so right! Actually, I like 'It is you who are wrong.'

Are we being awfully pedantic here?

@Brus - It's a bit late in the day, but I'm with donnahansen and EngLove on this one. If the "you" being addressed is one person, "who" refers to a singular person and takes "is"; if the "you" refers to more than one person, them it takes "are". I absolutely agree with your analogy with "It's me who ...", but with the opposite conclusion. As you yourself said earlier, "It's me who am (eg responsible for...)", doesn't sound right. And that's because nobody'd say it. "It's me who is (responsible for ...)" is the grammatically natural statement. Checking through Google books with Ngram shows absolutely no examples of "It is me who am" or "it's me who am", while finding a reasonable number of examples for the "is" variety. But I'm rather surprised you don't hear that "It's me who am ..." is ungrammatical, as you hinted at earlier.

http://books.google.com/ngrams/graph?content=It+is+me+who+am%2CIt+is+me+who+is%2Cit%27s+me+who+am%2Cit%27s+me+who+is&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=

In Practical English Usage, Michael Swan gives two possibilities for the "me" type:

It is I who am responsible (formal)
It is me that's responsible (informal) (that and who are interchangeable - WW)

And recommends a possible middle way - I'm the person who is responsible.

Oh no! Horrors! Did I write "It is me who ..." ? Too many beers. It is of course "It is I who am ..."

It (Subject) is (verb) I (complement, same case as subject, so "I" unless disjunctive "me" as in French "C'est moi"). "Who" introduces relative clause, antecedent "I" refers to 'me' so 'who' is singular, 'who' is the subject of its clause, and singular, and takes its number and gender from its antecedent, so is singular; so "who is .." can be the next bit. "It is I who is wrong." Something indeed sounds wrong.

'I'm the person who is responsible' is a cop-out.

I still like "It is I who am wrong." The subordinate clause verb then takes its person and number from the relative pronoun. I am uncertain if it is correct, however, as until this occasion I have never had occasion to use the expression.

@Brus - I know it's perfectly correct, but "It is I who am wrong" is too formal for me and personally I prefer "It's me who's wrong".

If Swan is right (and he is THE authority in my field), then in the original question both are correct (as subject and object form of "you" are the same); it's simply a matter of formality. But I still prefer "is" when addressing one person.

still confused about this one... doesn't the word "who" relate to the word "it" ? for me to use a singular verb?

Judging by its use in books, the plural is the norm; this is from Thackeray, ' "It is you who are cruel," cried Pen'.

I think in informal English, however, we might well say 'It's you who's wrong'; 'are' sounds a bit stilted somehow.

My explanation would be is that this is a cleft sentence where 'It' is an introductory device, the subject of 'is', and 'who is wrong' is a specific type of restrictive relative clause modifying 'you'. The verb should therefore agree with the subject of the realtive clause, 'you', not 'it'.

Compare with a couple of more obvious plurals:
"It's the Johnsons who have just been to Cypress, not the Smiths." (Not 'has')
"It's oysters that make me feel ill, not mussels." (Not 'makes')

Although 'Is it you who are' is the gramatically 'correct' answer, I'm increasingly convinced I'd normally say 'Is it you who's ...' or use a workaround.

A similar problem with a relative clause came up in class the other day in an exercise on tenses from a book called Grammarway Advanced. There was a question where the students had to fill the gap with a suitable verb in the appropriate tense, includinng the word 'ever':

"This is one of the best books that ................ on the subject"

The students were obviously meant to pick the present perfect passive of 'write'. And my first reaction was:

"This is one of the best books that has ever been written on the subject". But then I started thinking: the relative clause refers to 'books', not one, just as the relative clause above refers to 'you', not 'it'. So maybe it should be 'have', not 'has'. It turns out this one has been bothering people for centuries. Although Fowler thought 'has' here a blunder, it's been used by many good writers. It seems that 'one' is just too strong a draw for most of us; it's that oldidea of notional agreement taking over from formal agreement.

I think it's the same with 'Is it you who are'. Formal agreement favours 'are', notional agreement favours 'is'. And in spoken English, at least, notional is often more natural and idiomatic than formal or 'correct'.

a) "you're" is short for "you are" - "I hope you are well " sounds ok so the answere is "you're".
"Your" sounds the same but indicates possession (compare we - our / you - your) ; "I hope your health is ok" is correct.

b) Who is seeking? Answer: "our client"; singular or plural? = singular; therefore "is" is correct. Thus either: "Our client is seeking" or "Our clients are seeking".

c) "Our client seeks" is fine, just perhaps a little more formal in this context.

In “it is you,” what does “it” refer to? That is the key question here. A more direct way of constructing this sentence is: “Who is wrong is you.” In this case, you would not write “Who are wrong is you.” Why? Because it’s saying “The answer is you.” The answer is singular.

To reveal what is implied but not said, we can write the same sentence like this: “To the question of who is wrong, the answer is you.” Or, “The answer to the question of who is wrong is you.”

In other words, “is” should match “the answer” not “you.” If “It” were referring to “you,” the sentence would be a tautology: “You are you.” You would not write “The answer are you.” So, I would argue that “is” is the correct answer.

Hi Donna! I found a worksheet about simple present tense. The paragraph: ¨He lives in Chicago with his parents and his twin siblings- Denise and Mike, Who is 20 years old.¨ The paragraph is about the twin siblings.. it is Who is or Who are..? I am confused. Please help me!

Clearly, it should be "Who are 20 years old," since they are twins, therefore, plural.

I cannot believe that the French would have any doubt about which is correct. They would say: "C'est toi qui as [singular] tort", not: "C'est toi qui avez [plural] tort." Are the French more grammatical than we (us?)".

Dyske, you say it should be "is" because it matches "the answer". OK, but what if the number changes, mid-sentence: "It is they who are the problem." Doesn't that sound more natural than "It is they who is the problem"? "They" is plural; "the problem" is singular. Plural wins in this case.