This is as good a place as any to tell a story about a grammar disagreement that effectively broke up a local social group. To protect the innocent, let's say the group consisted of cousins.
It was a new club, and its logo was being designed. The first draft came back misspelled. But club members couldn't agree what the correct spelling was.
Group A said it was "The Cousins Club." They said "cousins" was an attributive adjective.
Group B said it was "The Cousins' Club." To them, "cousins'" was a plural possessive adjective.
Group C said it was "The Cousin's Club." They couldn't name the specific part of speech, and during the discussion demonstrated that apostrophe's belong in lot's of place's.
The club did not survive this disagreement. I believe they did get the logo designed, but there were enough hurt feelings from the discussion that all the original momentum was lost.
