I don't know about you, but I think everything surrounding Eugene Black is just a scam to reel Arbiter and possibly Chief in. The sick sister, the rough life at school, I think everything that has been brought up to develop Eugene's supposed "character" is just a scheme so when the big payoff comes, everyone will be shocked. So, yes, I'm calling it...
Eugene's past and life has all been a lie just to level himself with Arbiter's situation. That way, when Eugene decides to double-cross him, it can be quite the mind-f**k. If that happens, I'd say that Eugene will be the greatest Arby 'n' the Chief villain. Not only would he betray Arbiter, it could scar him for life.