Wow, that's such horrible, painful news to receive. I know how you feel, my dad passed away when I was 16 and I too had no real experience dealing with death. Death is a scary thing to confront, but don't let fear control you. About your dad and mom's reaction, I think people grieve in different ways; some people keep everything inside for a long time. Or maybe the full realization of what's happened hasn't hit them yet. You know, it's the craziest thing but sometimes I still can't believe what happened to my dad; I actually have to remind myself of what happened (not that I ever actually forget), I actually have to suspend my utter disbelief of what happened to accept it and this is more than four years later. I hope you find a way to deal with the loss and keep living life, and I hope your brother is finally at peace and free from his demons.
*edit*
Last piece of advice for you (and anyone): Love your family if you've got one.