According to grammar expert Mignon Fogarty, the host of the podcast Grammar Girl, here are two easy rules for pluralizing last names correctly.
How to Pluralize Last Names
Rule #1: A last name is always written out in its entirety. Think of it this way: It’s their name, so you can’t exactly change it, right? Rule #2: You never need an apostrophe when signing or addressing cards. (Apostrophes imply possession, which isn’t what you’re trying to do. You’re simply naming them in the plural.) These rules mean you should write out any last name in full, whether Williams or Garcia, and simply tack something onto the end. In most cases, you only have to add an s to the end of their entire last name—even if the last letter is y. So the Smith family becomes the Smiths, the Angelo family becomes the Angelos, and the Perry family becomes the Perrys. Exceptions: There are a few exceptions, however, which is where things can get confusing: If the name ends in s, z, ch, or sh, you need to add es. That means the Davis family becomes the Davises, the French family becomes the Frenches, the Hernandez family becomes the Hernandezes, and the Glaves family becomes the Glaveses. If the name ends in x, also add es—unless the x is silent. In that case, simply add an s. So the Felix family becomes the Felixes, and the Bordeaux family becomes the Bordeauxs.
