PERSONAL FAMILY PROBLEM. PLEASE READ?

i really dont even know where to start. but ill make it as short as possible. im 17, and my bro hes 20 and he has a problem. hes on drugs he doesnt go to work he doesnt go to school, doesnt do anything. i live at my gmas house w/ my mom and my little bro, and some nights he comes and some nights he doesnt he stays at his gfs house. this problem isnt new at all, its been going on for like the last 4/5 years. he steals stuff and touches things that dont belong to him. hes stolen from my moms pocketbook my gma, and he steals from me. im a tennis coach, so i work for my money and clothes. and b/c of him i lock up my closet. but he picks the lock and hes stolen like 200 from me, and he steals my clothes. and when u ask him about it all he does is deny it. just like eariler today, remember thishas been going on for years. i ask her mommy tell me what uve done to show that u dissaprove of what hes doing? b/c when this thing happens, my mom doesnt do anything the most she would do is just ask him about it and if he says idk or i didnt do it, thats basically where the convo ends. and when he steals stuff and i tell her she makes it seem like im bothering her. she always asks me, well what am i supposed to do? and im like y the f** is she askin me wut is she supposed to do? about her son stealin? i was like if u dont know wut to do then maybe u shud call somebody or ask for help who does know. cuz i say to her all the time i say what right does he have to touch my stuff if i bought it and he didnt help me pay for it, he doesnt even have a job. maybe i'm missing something? b/c i always tell my mom and gma that it makes me feel like they're trying to justify what hes doing and always makes excuses specially my gma she says well u know he has a problem. i say to myself ok yea he does but thats still no reason for him to do what he does. and one thing i said to my mom was u can tell him if hes gonna continue to steal my stuff he cant come back here, and her excuse is she cant do that bcuz its not her house (we live with my gma) but i think the truth is she just doesnt want to. but evrytime we let him in, its like ur givin him opportunity to steal some more stuff. & by u not doin nothin about it, ur only allowin it to happen again. when i try to talk to him he denies it, so i just dont talk to him no more, and at nites i dont let him in the house. i tried to call my aunt whos a social worker and she said to call the police and she couldnt belive that my mom was allowin this to happen for this long. but i know my mom wud never call the police on him though, but i dont c y not. and wen i asked her she sed when u become a parent youll understand. and i said to myself ok i see that ur trying to look out 4 him, but what about me though? at the same time, hes still stealing my money and stealing my clothes, and ur not doing nothing about it. so that makes me feel like shes choosin like what do i wanna do? not kick adonnus out or keep him in, and have him to continue to steal my younger sons clothes. and it seems like shes choosin not to kick him out. which isnt right and it isnt fair. so can somebody pleaase tell me what i/we can do? cuz im tired of this. maybe if u cant answer it here u can email me at lewisdreshawn@yahoo.com thanks. feels really good now that i vented all of that out