This may be long and complex, so I apologise in advance.
Background: My little brother (21) has Asperger's Syndrome. Before I start, I should point out that I do not think that his ASD is the reason for his awful behaviour, but at the same time, I do not believe you can separate the two. Everything is black and white to him; he is right and you are wrong and if you don't like it you can get lost. Because he is the youngest, and because his ASD made his school life a huge challenge, he has always been protected and sheltered by my mum (and me, I'm 9 years older so have always 'mothered' him too). He and my dad have always had a strained relationship (personally, I think my dad is on the spectrum too) to the point that, after an argument a few years ago, my brother has practically cut him out of his life and only tolerates his company for the sake of my mum, whom my brother adores. My dad tries really hard with my brother, tolerates his rude and selfish attitude in a way that he would not from any one else, helps him out financially etc but it makes no difference to my brother - in his mind they argued and now dad is dead to him. Even though the argument was trivial and both were at fault.
Anyway, my brother managed to get a flat from the housing association. He has no job and lives on benefits (his ASD means that he is not very employable - if a manager tells him he has done something wrong, but he thinks he is right, he quits because the manager 'is an arsehole who has got it in for me'). He is mixed up with a bad crowed, he smokes weed and walks and talks like he is some sort of 'gangsta', even though his upbringing couldnt be more different. My parents are working class, but we have always been well fed, well looked after, taken on holiday, bought the latest gadgets etc. They bought us up to work hard and be respectful. Because he lives off of benefits, my parents have furnished his flat for him. They buy him food every week and regularly supply him with new clothes and shoes when he needs them. Mum finds little jobs for him to do so that she can have an excuse to give him small amounts of money or top up his phone credit. There have been several arguments about his weed smoking so mum tries not to give him cash so that he cant buy it.
Anyway, to the actual problem. My mum found out a week or two ago that my brother had stolen money from them. She had a large amount of foreign currency left over from a holiday. She decided not to change it back and instead save it for the next year. It was in an envelope in the bedroom that my brother stays in when he goes to visit. He had been taking small amounts of the money here or there over a period of about 3 months. In his words 'I was wrong to pinch it, but I always feel so bad about asking to borrow money so I thought I could pay it back'. He stole £300. He knew he wouldnt be able to pay it back. My mum told him that he would have to pay it back and was going to ask him for a few pounds a week. He got all upset and left the house pretty quickly. The next day, he turned up with £300. My mum (and I) have asked him where he got the money from and he keeps trying to say that he had it stashed away. We know this is a lie - its just not possible. So, either he has sold the television and games console that my parents bought him for Christmas (this would actually be the best option), or he has borrowed it from someone and has no real way of paying it back, or he has done something criminal to get it. My mum is terrified that he has gone to a street lender or ripped someone off and will end up getting beaten up or killed. I am too, but I am also so fucking angry at him. He stole from my parents, two people who give him everything. When he told me what he did he acted like it was just a little mistake. He told me in a 'what am I like?!' kind of way. My mum will never, ever turn her back on him no matter what he does and he knows it. She hasn't told my dad because he will go mad and there will be another argument.
I, on the other hand, was so angry that I wanted to slap my brother and tell him to stop acting like an arsehole. I didnt though, because I know that if I did he would just cut me out of his life without a second thought. He doesn't have any kind of family obligation, it wouldnt upset him to lose his sister because he doesnt think like that, his brain simply doesnt work that way. I am scared that if he cuts me out of his life I couldnt help him if things got really bad (which I know they will because of the way he is living his life).
So, how do I help someone who is so fucking impossible? I am so scared that he is going to end up dead in a ditch. Either from drugs or violence. But, at the same time, he is horrible. He doesnt care about anyone but himself. He hurts the people who love him the most. What do I do?