Language expert Mark Liberman (of Language Log) admits: He is uninterested in punctuation:
Give me a choice between reading about the order of quotation marks and commas or perusing a random phone book, and I'll dive right into the A's.But then he dives right in to whether "fellow Americans" should be hyphenated.
The New Yorker, he points out, hyphenates fellow constructions consistently. But most other American publications do not, including the New York Times, the Washington Post and the Atlantic.
There are some rules to back up the hyphenation. This list of rules, for example, says you "use a hyphen to unify most compounds having brother, father, mother, sister, etc. as the first element." It gives such examples as brother-workers, sister-cities and fellow-workers.
I would never hyphenate such a construction, though. And I find it just as jarring as Liberman.