All through history, you can see where people, around the same time, have similar thoughts. Eg, Newton and calculus. Newton was a genius, and so was Leibniz.
http://en.wikipedia.org/wiki/History_of_calculus Does it matter so much who invented it? Both were brilliant minds.
It's not quite the same kind of case. Leibniz and Newton developed the calculus pretty much independently, and we give credit to both. The modern notation more resembles that of Leibniz.
People had been working on what would become Special Relativity for about three decades. Maxwell's Equations indicated that the speed of light didn't depend on the source of the light, and everybody knew something else that behaved this way: waves. They knew that if light were a wave, that Galilean/Newtonian relativity would break. Light was presumed to move through a luminiferous aether, and there should be an "aether wind" that affects light that could be detected. After the failure of the Michelson/Morley and subsequent similar experiments to detect such a wind to any degree greater than the errors in measurement, this was puzzling.
Lots of people contributed. Poincare' asserted that, due to MM, the principle of relativity should still hold and predicted a theory in which
c would be a limiting value. Other people were working on a lot of things. Fitzgerald suggested that the null result would be obtained if the aether wind pushed on a bar in such a way that it contracted along the direction of travel through the aether. Lorentz, who had come up with the same idea, realized that time would be affected as well. The math that they came up with, happily, was right, so to this day we refer to the transformations of SR as the Lorentz/Fitzgerald transformations.
Everyone, however, was working with the idea of the ether wind. This had problems. For one thing, the Lorentz/Fitzgerald idea was purely
ad hoc, or at least it was after the time change was introduced. For another, if the ether wind actually pushed on bars and clocks, it's hard to explain why it didn't stop the Earth and make it crash into the Sun a long time ago.
Einstein, however, suggested that the reason that the ether wind was undetectable was simply that it didn't exist. He realized that would only work if measurements of space and time themselves were relative. So he came up with what is now known as Special Relativity, just taking as stated postulates the principle of relativity and the fact that the speed of light didn't depend on the velocity of the source. (That it neither depended on the velocity of the observer can actually be derived from those two, but in any event, it was pretty well confirmed by Michelson/Morley.) Apparently, at the time Einstein was ignorant of Lorentz' work, but when he found out, he heaped lavish praise upon him.
So Einstein made this beautiful theory that only takes knowledge of the Pythagorean theorem to understand. Nobody else had been able to overcome the emotional prejudice that measurements of lengths and (especially) time were relative.
But he didn't get famous for that, and it's likely that someone else would have come up with SR in a decade or so. He got famous for General Relativity, which had no smoking gun, and which nobody else had thought of (though, once he got going, other people such as Hilbert and Noether helped out). But then it explained the precession of Mercury. And it's also a far greater achievment than SR.
And he also came up with the photoelectric effect and other quantum stuff, also in collaboration with others. This is why he got the Nobel prize.
Anyway, apart from the incredible, perhaps unprecedented brilliance and wide range of Einstein, it's a fairly typical scientific story. Everyone in the business knows who did what and apportions credit in a fair manner. Einstein deserved every millisimmons of groupie status he got.
Now, I personally think all those other people should be famous as well. But I'm not one of the people who are in charge of who gets famous.