While I don't think there's anything wrong with that type of situation, I would never personally be interested in being in it. I doubt I would be interesting in reading anything based on it, either, since it's not something I would personally be able to relate to.
The reason I wouldn't be interested is the sexual aspect. Sure, I can intellectually admit that incest is a social construct for the most part (yes, if you're having sex with relatives for the purpose of procreation there are other issues, but safer sex for the fun of it... nothing inherently wrong with it), but even the thought of seeing/overhearing my sibling having sex turns me off. I also wouldn't want my partners' sibling(s) to hear us having sex. It happens on occasion when we're on vacation and staying with family, but on a regular basis, no thank you! When I'm involved with two people, I enjoy group sex if they're both into it. Them being brothers or brother/sister? Wouldn't work for me. Them being involved with my sibling? Wouldn't work for me.
That's my view on it. Take from it what you will.