What to Know
Name pluralization is similar regular words. Add -es for names ending in “s” or “z” and add -s for everything else. When indicating the possessive, if there is more than one owner add an apostrophe to the plural; if there is one owner, add ‘s to the singular (The Smiths’ car vs. Smith’s car). If the possessive involves a last name ending with “s” or “z,” you can add either. Special rules apply for classical and biblical names.
The plurals of last names are just like the plurals of most nouns. They typically get formed by adding -s. Except, that is, if the name already ends in s or z. Then the plural is formed by adding -es.
the Smith clan → the Smiths
Jill and Sam Clarence → the Clarences
Mr. and Mrs. Jones → the Joneses
the Fernandez family → the Fernandezes
the Kennedy clan → the Kennedys
the Daley family → the Daleys
Possession & Names
If you want to talk about something that belongs to more than one member of a family, you start with the plural form and add an apostrophe to show possession:
the Smiths’ car
a party at the Fernandezes’ house
the Daleys’ driveway
If you want to talk about something that belongs to a single person being identified by last name, you follow the usual -‘s rule for most names:
the car that belongs to Smith → Smith’s car
For names that end in an s or z sound, though, you can either add -‘s or just an apostrophe. Going with -‘s is the more common choice:
the car that belongs to Jones → Jones’s car or Jones’ car
Special Rules for Classical Names
For classical and biblical names there are other rules. For names ending in s or es and having two or more syllables, you usually just add an apostrophe. If the name is only one syllable, add -‘s.
The names Jesus and Moses are always made possessive with the apostrophe alone:
Silent Ending Letters
The usual way to show possession with a name that ends in a silent s, z, or x is with -‘s.
Didier Deschamps’s career
Josquin des Prez’s music
Eugène Delacroix’s paintings
View original source at merriam-webster.com