The Mystery of the Multiple Brotherhoods of Evil

With X-Men and the Doom Patrol already so similar and published close together you'd suspect industrial espionage (although, I'd say the DP are far closer to the Fantastic Four, right down to an orange strongman), they really didn't need even more common ground. But in January of 1964, both teams were introduced to a supervillain team called the Brotherhood of Evil (the X-Men added "Mutants"). No, really, look:

Coincidence? Not really. See, some five years before, THIS book was published:

Not only was it one of the first fact-based books about the mob, but it has seen gone through multiple editions. Crime fact and fiction would surely have interested comic book writers, but even if neither Stan Lee nor Arnold Drake read the book, it seems the title was adopted by a major newspaper headline, on an article about organized crime, around the time both issues would have been plotted out.

Sometimes, there's no such thing as a coincidence.