Seems allmost the most logical one to me. They both have had or have a monster inside, they both have a past where they did terrible things, they both tend to keep an emotional distance and are very guarded from others, both feel that they have to control theyre own emotions, they both have a very low key, allmost sarcastic wit and sense of humor...
Its perhaps for different reasons, but they have a lot in common. And at the same time, they are a bit of oposites, him being the more shy and her being the most proactive one, and as the saying goes, oposites atract each other. I think if you look past the surface, that combination of oposition and relation makes for a very believeable relationship.
Dont get me wrong, you are entitled not to like it, of course, but i dont think its as odd or out there as people are making it out to be if you look close enough.