How to pluralize surnames ending in short vowel then s?

I've seen on this board that these are the rules: for certain ending letters - which include s - to add es to pluralize, and add only s to the rest. The rules say never change y to ies. And of course never use apostrophe!

But I have a friend whose surname is Kos, pronounced "koss". Should her family be "the Koses"? That looks like it would rhyme with the pronunciation of "the roses". My gut says double the s, but maybe not if we don't change y to ies...

http://grammarist.com/style/last-names/

Plural last names

Making a last name plural should never involve an apostrophe. The members of the Johnson and Smith families, for instance, are the Johnsons and the Smiths, not the Johnson’s and the Smith’s.

Last names ending in s are no different. Most nouns ending in s are pluralized by adding es. This applies to last names as well. The members of the Edwards and Doss families are the Edwardses and the Dosses, not the Edwards’s and the Doss’s. Your spell check might disapprove of the correct forms, but spell check is wrong on this matter. If you understandably find words like Edwardses a little too awkward, consider rewording to avoid the plural. For instance, the Edwardses can become the Edwards family or the Edwards household.