Ok, never actually hade to deal with this but hypothetically;
what do you do when you want to indicate possesion by a number of people when their names end in s.
Annie's room (ball belonging to Annie)
Annies' room (ball belonging to Annies, plural)
James' room (ball belonging to James)
?????????? (ball belonging to James, plural)
Pat Morris's car is silver.
Pat and Pete Morris also have a cut dog.
The Morrises' dog's name is Morty.
(Your examples were hard to follow because you uses first names. It's hard to imagine a situation in which you have two boys names James, and you want to talk about something that belongs jointly to them, and that you refer to them and "the Jamses.")