I think they all read more naturally in the plural.
Between them, multiple people have multiple... whatevers.
Two people have two brains, two married men have two wives.
You can make the reverse argument: Married men cheat on their wife. Do they all share the same wife? People, use your brain! Do they have one brain that they must share?
The exception is "food" which does have a plural form, but in that sentence, it's not countable, so just use "food."