How does Lady Macbeth and Macbeth's relationship facilitate his
descent into madness?

Singular third person pronouns are “he,” “she,” “it,” “his,” “hers,” “him” and “her,” and third person plural pronouns are “they,” “them” and “their.” the number of people to which you are referring should always match the pronoun you choose (“he” to refer to one male, “they” to refer to more than one male).