names ending in s: possessive
James’s vs. James’.
Add ’s to a singular name that ends in s: James’s book, Jesus’s name, Socrates’s trial. For a family, form the plural first, then add the apostrophe: one Davis, two Davises, the Davises’ house. See also apostrophe possessive.
Examples
Use Davis’s truck (one person named Davis)
Use the Davises’ truck (the Davis family)
Avoid Davis’ truck (apostrophe alone after a singular name)
Many newspapers and magazines put the apostrophe alone after a singular name ending in s, as in James’ and Jesus’. Readers see it so often that it can look correct, but it is not the standard form.