When Will He Learn

I haven't quite figured out why my other brother hasn't grasped the fact that what he does isn't right and that he hurts our family with the actions he does and with what he chooses to do with his life. He doesn't seem to make the right choices with things and always gets caught up in all the bad. It hurts my parents so bad. They can only do so much and deal with so much till they almost break. But my brother doesn't have much remorse in regards to the fact of what he does. He will feel bad for a day or two but its always back to what he always does. It never fails. I wish he would just change how he is and be who I know he can be. He's a brilliant man, but he doesn't put his smarts to work. I think he lacks some common sense. We all think that in our family. And I, myself, think that he can't tell people "no" either so all his friends take advantage of him and use him for whatever they can. He may not admit that, but I know how he is. He will do anything for anyone, which isn't always a bad thing, it can be good, but when people use you in evil ways that isn't good at all. But he doesn't know the difference between the 2 I'm pretty sure. For some reason my brother will say he's going to do something really quick, take my moms car and be gone for days. And while all this is going on my parents swear thats it and that they've had enough, he will return and they talk it all out, but it starts all over again in a matter of days. I just don't understand...will he ever get it?