Samuel Kirkham, English Grammar in Familiar Lectures
“ Relative pronouns agree with their antecedents, in gender, person, and number; as, "Thou who lovest wisdom;" "I who speak from experience."NOTE. When a relative pronoun is preceded by two antecedents of different persons, the relative and the verb may agree in person with either, but not without regard to the sense; as, "I am the man who command you;" or, "I am the man who commands you." The meaning of the first of these examples will more obviously appear, if we render it thus: "I who command you, am the man." ”
