You have friends named Jennings and Reynolds—the Jennings family and the Reynolds family, also known as the Jenningses and the Reynoldses. (Those are the only grammatical plurals for those names.) A large group is having a get-together at the Jenningses’ house. Or is it at the Reynoldses’ house? Either way, it’ll be delightful.
Last week, a correspondent wrote to us at LawProse: “Would it not be equally tenable to consider family names (ending in s or otherwise) as collective nouns, so that the Jones’ house would be sufficient?” The answer is no: you can’t put a possessive apostrophe on a singular name with a plural meaning.
But just as you could say the Garner house or the Jefferson house, you could say the Jennings house or the Reynolds house, using the last name attributively (as grammarians put it). But this sort of attributive use can’t have an apostrophe.
The rule for a plural possessive is to pluralize first, and then add the possessive apostrophe: Garner makes the Garners (plural) and then the Garners’ house (plural possessive); Sinz makes the Sinzes and then the Sinzes’ house; Voss makes Vosses and then the Vosses’ house; Walters makes Walterses and then the Walterses’ house. If you don’t like the plural possessive on names ending in s, then try the attributive use (the Walters house)—but remember not to use an apostrophe there.
What about the singular possessive? It’s preferably Jill Sinz’s house, Amy Voss’s house, Rob Walters’s house. But just to confuse things, the singular possessive has an alternative form that is also correct—without the s after the apostrophe.
But the plural possessive has no double possibilities for correctness. As a matter of convention, it simply never has.
Do you now feel fully in possession of the facts? To read more about this matter, try these resources:
The Chicago Manual of Style § 7.17, at 422 (17th ed. 2017).
Garner’s Modern English Usage 712–13 (4th ed. 2016).
The New York Times Manual of Usage and Style 265 (rev. ed. 1999).
The Redbook: A Manual on Legal Style § 7.12, at 143 (4th ed. 2018).
Words into Type 477, 479 (3d ed. 1974).