hi, i'm so sorry to hear about your troubles but im glad you are reaching out for help. there is not much more you or your mom can do to help your brother or father. they have to do it for themselves. i think you mom did the best thing for the both of you when she allowed him to choose where we wanted to go rather than bring him home with you guys.
unless he is allowed to suffer the consequences of his own actions, it will be much harder for him to reach his bottom and have the desire to seek help. i think its good that he is finally deciding to go to rehab, whether he is serious or just need a place to go. there he will learn tools to help him in his recovery. it will still be up to him if he is to get better or not. rehab is not a cure all, but its a start. detox and rehab is just the beginning, absence from the drug allows time for the brain to clear. it will be totally up to him whether he stays clean after that but you can get better even if he chooses not to right now. his behavior is common with addicts.
time for you to take the focus off your brother and father and take care of you. addiction effects all who loves the addict and they need help too. believe it or not, the best thing you can do to help your brother is to do what you need to do for you, and that goes for your mom too.
keep reading and posting here as much as you like. the addict in my life is my hubby and when i first came here, i was just about insane. alanon, naranon are support groups for family members. they are so helpful and supportive, maybe you can search your area for a few meetings and invite your mom. others will be alone shortly so please stick around and read the little stickies at the top of the forum page. learn all you can about addiction and co dependancy.