I'm not convinced you can point to any one source and go "that's where this comes from and they're all inspired by that." From where I'm standing it just seems like the most conducive way to format a soulmate situation. Just seems to be one of those pervasive things, kinda like those dystopian stories where a dome covers an area and everyone inside turn against each other, anything set in an academy of any kind or anything featuring a "chosen one." Broad concepts and tropes kinda become public domain after they make the rounds a few times, if that makes sense.  

From a practical standpoint, it would be difficult to have some kind of soulmate-style, fated-to-be-together type setting [i]without[/i] some kind of identifying feature such as a mark. Obviously you could work something out without it, but what can I say? People like the trope!