JohnInKansas says, "Attempts to introduce artificial postulates and possibilities (even when the question is only partially formed in the original statement) merely indicates a reply from someone not really interested in the logic."

I disagree. The question must be completely formed in the original statement; otherwise it is logical to introduce postulates and possibilities not forbidden by the original statement. If, in this case, you mean to say that one must assume that the twins may only answer one question by saying "yes" or "no", even though the original statement does not include this information, I'd have to respond that that in itself is faulty logic.