What should I do with my family?

I'm at a loss with how to fix the problem with my family. As for my mother, she is too trusting with bad people. She believed everything my father has said, like when my father said to kick out my brother and live on his own because he was a lunatic, she believed him and kicked my brother out. My father d my sister and divorced my mother. Now for my current situation, I live with my other brother and my mom, my brother who's 24, I'm 15, is more of a baby than myself. He whines when I say he needs to control himself when he's just talking trash. On the plus side, my mom has learned not to trust people so much, but she still takes my brothers side (the 24yr one) because he pays her rent while she needs financial help. The bottom line is, my mother keeps her mouth shut since my brother's paying the rent. And my brother himself acts so mean and baby-ish. He'll insult and shove anyone who tries to simply hug him. Which my mother cries when that happens. My 24yr old brother is going to therapy, however it doesn't seem to be helping too much. My family issues have put me down, though I just want whats best. I feel as though despite me being the youngest amongst the family, I should try to control their barbaric actions. The only problem is because I'm still underage, they just laugh when I say go to your room or stop what your doing. I'm at a loss at what to do with my mother and brother. Thanks for any help.