Bobby

I was a little bit confused about the oldest brother's character, Bobby. I know he wasn't the brightest of the 3, and that could partly account for him being so naive as to join a violent gang. But I could've used some more explanation, about his nightmares for instance. And apparently he also seemed to remember his dad different from what he really was. So obviously he had some issues. But what caused them? I can't really remember why, because it's been a few weeks since I saw the film, but the scene in which he smashes the skeleton raised questions with me too. I didn't quite understand why he did that. I thought some things needed a little more clarification in the film, but I'd also be very happy if someone reading this forum could provide it.