There's a finite number of story ideas, and it's inevitable that different people will coincidentally hit upon the same ones. It happens so routinely that "We're already doing a story like that" is the number one reason why freelance TV pitches or magazine submissions get rejected. So, yes, it's most likely coincidence -- or convergence, people working in similar fields drawing on the same pool of concepts and tropes and thus inevitably combining them in similar ways. I'm sure there are a ton of old horror/SF comics that have gimmicks in common with Twilight Zone episodes or the like. There are only so many ways to scare people. The loss of identity, the idea of being forgotten and leaving no mark on the world, is a pretty natural one.
