Question: Three people were getting married to each other,  

   Though polygamous they were not.

All men they were in the marriage,  

   Though homosexuality was not in their minds.

They three share two parents,  

   Though they detested the notion of inbreeding. (And this was not, in fact, a consanguineous marriage)

Who are these men?

Hint 1:

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>  The first line makes you assume more than has been said. The "people" referred to "are" not what you assume "them" to be.
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Hint 2:

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>  45 chromosomes are identical (Not a single difference, even on the atomic level) between the "three men".
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Hint 3:

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>  Hint 2 does not say that the 46th was different. And two of the "three men" were the same person all along.
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Hint 4:

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>  Two of the men are the same person. This is a different hint from hint 3.
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Answer: 
Partial Answer! Could it be something in the form of: 

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>  An alliance? With three leaders that are all male, of three countries that all originated from one original country? 
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Nothing comming to my mind, but someone may be better at history than I am if this is the correct path.
My best guess :

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>  A man with multiple personality disorder had a sex change and married his adopted brother. The "marriage" is a genuine marriage, but is between a man, a (newly-made) woman with the same parents but no blood relation, and the male alter-ago of the transexual. No clue about the chromosome part, maybe part of the surgery involved cutting one off.
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Just in case this is somehow not the correct answer (though I wrote this before reading the 3rd hint...),

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>  I *do* think two of the 'men' are the same person, somehow. I think in fact 46 of their chromosomes are identical and the 45 reference is a red herring. If they're identical to the *atomic level* surely it's impossible for them to be two different people?
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Also,

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>  Pretty sure sex change is involved somehow. The question even says at marriage they *were* men, which is ambiguous as to *when* they were men.
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