angry brother-need help with him

So where do I start. Anger has been a problem in my family for years. It comes from my father's side and I know that my siblings and myself all suffer because of it. I am the oldest and have had my fair share of dealing with an angry parent, my middle brother has trouble expressing his own anger, and my youngest brother is the worst of all. He is angry all the time and everyone now has to deal with his anger problem. My father has calmed down quite a bit since his son now assumed his role and the sad part is that I think my father is sympathetic toward his anger. My father thinks we all need to approach him differently. All of a sudden he is a physcologist! My mother. baby sister(she's only 9), and myself catch the brunt of it. He hates us. He yells at my mother all the time for god knows what! He now yells at my baby sister for being a little chubby-something he's stuggled with his whole life! As for me-he hates me most of all-I am sooo stupid and do not know ANYTHING. No matter how often I try to help him and talk to him about things-he's good guy for a day and flies off the handle the next. Today for example I invited my baby sister and my baby cousin to come to my pool with my mom who is going in for surgery tommorrow. My parents were away all summer and I wanted to spend some quality time with her...when who shows up to my house- my brother becsause he's out of a job(he can't seem to hold one down). He doesn't even say hello to me, ran away when I joked around with him abouit helping me do something, I'm 6 months pregnant and need help fixing around the house, and goes out by the pool! I go out by the pool and he's yelliong at the two kids-of course! I mean cursing at a nine year old like thats normal. So I left him alone and said not to use that language at my house. Then he takes his shirt off and lays by the pool. Later on I ask if the pool is filled and he tells me the filter is broken in a condescending tone. I told him that it's not broken it's the water level that's low and that is why the filter hasn't turned on. He proceeds to tell me that I know knothing and that I am sooo stupid. Then, he walks away from me, into my house as if it is his own and shuts the door on me. So I go in and shout at him and tell him that he shouldn't talk to me like that in my own house. SO he proceeds to go on and say how stupid i am and how he needs to get out of my house! So he leaves my mother and the kids stranded, takes the car, the kids have no carseat to get home in... I mean he makes the rules up on his own without thinking of anyone else. He has noo respect for others or himself and it is so self destructive. My husband is a very successful guy and so am I and we've gotten him 3 jobs so far because we thought that we could help him and he hasn't been successful at any one of them. He got fired from one because no one liked him! I mean he was making 50k's to start, he's only 23, and he got this job handed to him, when he got fired i was suspicious but never said anything. My husband finally told me the reasons why and I promised to never tell my brother because my husband asked me to. It wouldn't help telling him anyway because he'd never believe us that people don't like him. He blames everyone else, everyone is out to get him. That is his conspiracy theory. Anyway I need tips on how to deal with him. This argument was the second we've had this summer and I am considering distancing myself from him for good. Keep in mind that I am not the only one who is affected by his anger. My mother, and my baby sister also suffer. It seems he hates us the most and we care for him the most. Also, he is very close to other family members who have big anger problems. I guess birds of a feather do flock to gether. Anyway-I am very upset about this and would appreciate any advice. ANYTHING! Can you answer some of these questions:
How do I get my father and mother to see that they enable his behavior?
How do I protect my baby sister from his hurtful comments about her weight?
How do I assert myself without setting him off?