my brother is emotionally exhausting my mom.

My mother had children with someone who had mental disorders.  Apparently it's just bipolar disorder but I think it's more than that. My brother inherited something from my dad, I don't really know what but he isn't right. He's been 'tested' for bipolar, doesn't have it. But he is, exactly like our father. The best way I can explain it is.. Imagine there is a block in all of our heads that has logic, problem solving, a filter, empathy. He doesn't have that block. He doesn't care about consequences. He can lie to your face about something he knows you know is true and believe his own lies. He does not give a single flying shit about anyone but himself and if it doesn't benefit him he won't have shit to do with it. He's been on medication his entire life because he's had extreme behavioral issues... I don't know how my mom did that or how anyone would have done it. He makes me never ever, ever want to have kids ever because i have an extreme fear my kid will come out with our fathers genes and it'll be like my brother. He's been on medication and that literally helped nothing. Psychologists, counsellors. He's 17 now and his last counselor quit and won't have anything to do with him because he was so incredibly shitty to her. I can't with him, I avoid him at all costs because I literally cannot stand him. My mom came to me today and just started bawling and spilling her guts "I am so tired of him I want him out of my house he is so miserable to be around and I am exhausted and I don't know what else to do" like for my mom to say that about her own kid, damn. Shes a good mom but he's defeating her.  

He is verbally abusive to her, he manipulates her and steals her money. He also starts fights with our younger kid siblings and hits them like he is 17 years old and his younger siblings cannot be left home alone with him at all ever because he will end up hitting them. He has to be supervised with them at all times. He is 17 fucking years old.  he doesn't give a shit what she says. Tells her what he is and what he isn't gonna do. Tells her to go fuck herself. I don't even know what to do anymore and I don't know what to tell her. 

He is not stupid or slow, he knows what the fuck he's doing he just doesn't care. With the way he's going about his shit, he's gonna end up in jail. I am tired of my mom being mentally and emotionally defeated because of him and I just don't know how I could help her.