<p>Let me put it this way. There are two ways of looking at this.</p>
<p>1) The simplistic, familiar, popular, and obvious way. The noun or pronoun closest to the verb determines whether the verb is singular or plural because that’s the rule and it sounds best.</p>
<p>2) The unbiased way. We don’t say, “Either John or his parents is” because that is biased toward John. Technically speaking, we should not say “…are” either because that is biased toward parents. However, since, obviously, we have to use a verb and settle down with either a singular or a plural one, we pick the one that sounds better (“Either John or his parents are”) and that is correct. Now, “Either he or you are” is certainly biased toward you because he is not plural and does not otherwise require a plural verb. “Either he or you is” is not biased toward either construction because both constructions are singular; therefore, it is reasonable to say that it is correct.</p>