“Who, instead of being useful members of society, they are pests to mankind.” Here the verb are has two nominatives, who and they, each representing the same subjects of discourse. One of them is redundant; and by the use of both, the expression becomes solecistical, there being no verb to which the relative who can be a nominative.
“My banks, they are furnish’d with bees,”
is faulty for the same reason, though here, perhaps, the poetic licence may be pleaded in excuse.
“It is against the laws of the realm, which, as they are preserved and maintained by your majesty’s authority, so we assure ourselves, you will not suffer them to be violated.” Which is neither a regimen nor a nominative to any verb; the sentence, therefore, is ungrammatical—Them is redundant.
“Whom do men say that I am?” The relative is here in the objective case, though there be no word in the sentence by which it can be governed. In such inverted sentences, it is a good rule for those who are not well acquainted with the language to arrange the words in the natural order, beginning with the nominative and the verbs, thus, “men say, that I am who,” a sentence precisely analogous to “men say, that I am he,” the verb requiring the same case after it, as before it. Hence it is obvious, that it should be, “Who do men say that I am?”
“Who do you speak to?” It ought to be whom, the relative being under the government of the preposition, thus, “To whom do you speak?”
“Who she knew to be dead.”—Henry’s Hist. of Britain. Here also the relative should be in the objective case, under the government of the verb, thus, “whom she knew,” or “she knew whom to be dead.”
“Than whom, Satan except, none higher sat.”—Milton.
“The king of dykes, than whom no sluice of mud,
With deeper sable blots the silver flood.”—Pope.