Q. George Wilkens is a character in my novel. (Yes, I know I should have named him something without an “s” as the last letter!) My question is, Which is correct: “George Wilkens’s house” or “George Wilkens’ house”? After a study of several different sections of CMOS, I think that the former is correct. Can you verify that for me? Thanks.
A. You are right. Chicago adds an apostrophe and an s to form the possessive of most singular nouns, including singular nouns that end in s—a rule that extends to proper names. Plural nouns, including plural names, add an apostrophe only. (See CMOS 7.16 and 7.17.) To clarify these rules, let’s compare two different Georges, one who spells his last name with an s and one who doesn’t:
George Wilkens: George Wilkens’s house [singular possessive]; the house where the Wilkens family lives; the Wilkenses’ house [plural possessive; Wilkenses is the plural of Wilkens]
George Wilken: George Wilken’s house [singular possessive]; the house where the Wilken family lives; the Wilkens’ house [plural possessive; Wilkens is the plural of Wilken]
Though Chicago’s rules are logical on paper, a name like Wilkens—which looks and sounds like a plural—can be confusing no matter how it’s treated. To avoid complicating things even more, maybe don’t give George a French pal named Georges (the possessive of which would be Georges’s; see CMOS 7.18).