When a proper name ends in “s” and we have to make it plural or possessive, it seems it is always a bit jarring.
There are several things to keep in mind:
First, when a surname has the word “the” in front of it, it is always plural.
…I saw the Cohens when I visited D.C.
…The Johnsons joined us for dinner.
Second, when a surname ends in “s,” the plural form adds “es.”
…I saw the Joneses when I visited D.C.
…The Hollises joined us for dinner.
Third, when making a surname that ends in “s” plural possessive, make the name plural first; then add the apostrophe.
…It is difficult to believe the Wilsons’ story.
…It is difficult to believe the McIntyres’ story.
…I rode with them in the Rosses’ car.
…I rode with them in the Hodgeses’ car.
When using a surname as an adjective, there are two equally correct ways to say it.
…He is currently living in the Nelson house.
…He is currently living in the Nelsons’ house.
…He is currently living in the Wells house.
…He is currently living in the Wellses’ house.
The distinction in the latter case is often diffcult to hear and particularly so when the next word begins with an “s.” Think “passenger side” versus “passenger’s side.”
(And, of course, I have to point out that I married my wonderful husband in part so that I would have that really cool name to use in these examples.)