This post isn’t about who owns that crummy bar downtown. It’s about using apostrophes when more than one person owns something (although, we could be talking about that crummy bar). Look at the following sentences:
1. John and Bill’s crummy bar downtown is doing well, despite its location.
Why does only Bill get an apostrophe showing ownership? When two or more people own the same thing, only the last person mentioned gets an apostrophe. That’s the rule.
2. John’s and Bill’s wives are very good friends.
Presumably, John and Bill each has his own wife; they don’t share connubial bliss. Therefore, each man gets his own apostrophe (along with his own wife).