Auxiliary use?

Is it possible to use auxiliary after auxiliary for example is after are , now read these printed document from regardable book and compare or judge why he wrote that:

a part of document:
The company is called International Plant Reaearch Institute ( IPRI). It is based at SanCarlos, near San Francisco.The man behind it is Mr. Martin Apple, better known for his work at the University of California on treating cancer in animals. He has 12 scientists associated with his new project. Who they are is for most part kept confidential, even among the 12.
now look the underlined sentence contaun two verbs ( are , is ).
1- is it right ?
2-If it is right what does it mean?

Hello MMA,

The underlined phrase is correct, though perhaps could have been better worded.
You need to split the sentence like this:
Who they are / is for the* most part kept confidential.

*The definite article is needed here, but is missing from your quote.

This sentence means:
The identities of those 12 scientists are kept mostly confidential. Even they don’t know the identities of the others.

What’s going on here is that you have a noun clause as the subject of the sentence.

“Who they are” is a noun clause, meaning a clause that is being used instead of a noun. So if you put the subject in brackets, you could replace “who they are” with other types of noun phrase. For example:

[Who they are] is for the most part kept confidential.
[Their identity] is for the most part kept confidential.
[That information] is for the most part kept confidential.
[It] is for the most part kept confidential.
[What their names might be] is for the most part kept confidential.

Those forms of “to be” are not auxiliaries in that sentence. They are linking verbs. They are not helping to form other tenses or create the passive voice; they are linking the subjects to information.

Thank you both users friends , that you say is right , and not anyone could understand the method of writing , yes linking verbs .
The semantics here played role.