In a case where there is more than one plaintiff or more than one defendant, diversity of citizenship does not mean that one plaintiff must be a citizen of a different state than one defendant. All of the plaintiffs’ citizenships must be different from all of the defendants’ citizenships.ven if the defendant raises a question of federal law, for example, in its answer, if such a question is not raised in the complaint, the court does not gain subject matter jurisdiction on the basis of the defendant’s answer.