With anybody else posting, I would know it was just a hypothetical question.  But with your client base, there is a good chance it could be a real question.

And the answer is - the U.S. government considers conjoined twins two people. They each get a social security number, drivers license, diplomas.  And according to a non-technical source, yes, one can claim the other as a dependent.

I would say the chance of this post being removed is 50/50.