Use of the apostrophe

I think there are exceptions, and those two are some of the exceptions. According to Michael Swan in Practical English Usage, sometimes we add an apostrophe to a singular noun ending in 's' in older and foreign names. But just sometimes, Dickens is still written Dickens's novels. Tough question, Maj.

Also about the nouns, that would be called joint possession. If two nouns jointly own a possession, then you add 's to the last noun. If two nouns have individual possession of the noun, then you add 's to both. (I said 's, but you should use ' whenever necessary).

Example.

Adam and Eve's garden.
It is either Adam's or Eve's decision.

In the first sentence, Adam and Eve co-own the garden. While in the second sentence, Adam doesn't own Eve's decision, nor Eve does own Adam's decision.

then there is the surname James. if Mr. and Mrs. James James (or Robert James, if you prefer) invited people to their home, the invited guests could say, "we are headed over to the Jameses for cocktails." (here it is a plural, not a possessive!)

Then it would be "the Harpers' bar" - In this case, Harper was given as the name, like the name of a grandfather or something.. John Harper's bar etc..

It'd be "The Smiths"