I've been posting on this site for a while now, and throughout my time here I occasionally see these romance rps based around people having a mark on them that connects them to their soul mate. It's not as though it's a huge trend but there's enough of a pattern for these rps to peak my curiosity because, despite taking place in multiple sections and being created by multiple users, they seem to have an established set of rules they tend to follow. People are marked, they're fated to fall in love with the one that shares there mark, if one of the pair dies the mark goes grey etc etc...

What I'm wondering is what is the source for these rps? Is this a standard RP type on the internet? Was there an anime or fantasy novel that used this as a premise? And if anyone has played in them, did it go well and stay compelling?