Brother refuses help and expects me to take care of him?

This has been a battle for months at this point.. I lived alone from 18-22(I'm 23 now). These last few years, my brother has lived with our mother, from when he was a minor until just a few months ago. He's been on some hardcore drugs, addicted. And him and mother would argue frequently. He's not exactly a pleasant person to be around a lot... I love him, but I kept my distance of course. I stayed away from all of my family, it was just me.

Well, now... My mother convinced me finally to let her live with me and she would take care of the bills so I could save up money for myself, to leave and live wherever I want really. (This house is a long story so I'm not gonna share that here..) Right before she moved from her apartment, my aunt offered to take my brother in, an adult at this point, but young. He was about to be 12, this was during Christmas 2022. He was going to stay there with my aunt, but ended up staying with my mother on and off until she moved here where I am, basically.Since she moved in sometime late February, early March, I've been having to deal with ALL the family drama. My aunt is a psychotic, bipolar, and just awful but pretends to be sweet in person. My uncle might as well be the same. Both drug addicts, both mean behind scenes. Completely toxic. They were still housing my brother at least, but you can imagine the environment. I mean, just picture 3 m*th addicts living in one small space. (They were the ones that gave my brother drugs by the way.)For the last couple months, my mother and I have been trying everything we can to help him stop the drugs and to help him find a place to stay. I even offered my place if he ever needed a few nights away. About 2 months ago, I think, my mother had found him a rehab program. It would have been a better place than my aunt's and uncle's. And it would have given me the space I need to take care of myself. He agreed to go and I allowed him to live with me for a few weeks until the day the program person was back in state. Even through all of this time, he was still lying and doing drugs, even IN MY HOME. This was one of the major reasons I've always been against him and my mother both coming to live with me. The days go by and we can finally drive him a couple hours away to the rehab location.. My mother drops him off, comes back home. Turns out, he left. He was just wandering around the town. He didn't even stay one night in rehab. Apparently they have a no lock policy.. people are free to leave whenever basically. He wasn't even willing to stay for one night and TRY to get clean or get on his own feet. There's a lot more that happened the next few days.. but I don't want to really explain all of it.

Few days later, he's back living my aunt and uncle because even though they can't stand living with him, I guess they will feel bad if they turn him down? Even after they kicked him out and everything. I'm really not sure what their motives are. He's been going to my mother's work lately and then of course, she brings him back here because she doesn't know what to do and she wants to take care of him. He gets dinner and stuff when he's here and then he leaves back to my aunt's. He and I spoke a bit after the rehab incident.. I was very disappointed in him, and he broke the deal with had. (Being that he could stay with me for a few weeks if he went to rehab and tried.) I told him then that he was not to stay at my place anymore, but if he wanted to shower or eat here every now and again, that's fine.Now let's get to tonight...He went to mother's work again, stating that he told my aunt he was leaving and he told my mother he was going to stay with his grandmother. Our mother contacted his grandmother and she had no idea what he was talking about. She said my brother hadn't spoken to her in a couple weeks, and that he couldn't stay there with her and her husband because "all hell would break loose" or something similar to that. Our mother messaged my aunt asking what in the world happened, and my apparently my brother told my aunt and uncle that he was going to be staying with ME. I'm not exactly what he was thinking would happen lying to everyone about staying anywhere.. but anyway. Mother brought him back here to my place. And through all this time today, no one even messaged me once.. I woke up and he was just here, knocking on my bedroom door. He didn't message me, our mother didn't message me, not one single text. I was angry, as you can imagine. But I stayed calm, was nice. I wanted to let him rest for a few hours and at least eat dinner and then figure out what he was planning on doing. His plan was to go back to our aunt's place and sleep there or outside if they didn't let him in. Hours go by, and it's time for my mother to drive him back to our aunt's house. He disappeared apparently, and I had no idea. I thought she just drove him back, but that wasn't the case. And now, just before I started typing this... He came inside my home and knocked on my bedroom door. I was completely stunned. I thought he was at my aunt's. He told me he walked over there and they didn't answer so he walked back to my place. I don't find this believable to be honest, because I think it would have taken him more time to walk all the way there and back... so I honestly have no idea where he went and what he was thinking. I went and woke up my mother and had a somewhat calm explosion on the both of them. I told him I love, but reminded him that he can't stay here anymore, I told him that he isn't my responsibility, that he's an adult and he needs to figure out what he's doing. I told him that every time someone offers to help, he refuses and mentioned that he even wouldn't stay one of the best rehab programs here. I can't remember the full conversation because I was upset and crying and just talking.. but basically that he needed to get his life together because we can't baby him anymore.I told my mother that I was upset with her because she kept bringing him here, without even telling me. I mentioned that I know she loves him and wants to take care of him, but that he isn't on us, he's an adult. We all just stood in silence for a few minutes....She was going to drive him back to our aunt's place, but when we all went outside, he just started walking away onto the street. I have no idea where he's going now... I don't know why he wouldn't just talk to us or at least go back to my aunt's where they may give him shelter, or ask one of my mother's friends in the neighborhood. I don't know. I don't understand his thinking.. and honestly I think it's clouded with the drugs. Heavily.

But anyway... I guess I'm looking for some advice on how to help someone who refuses help? I don't know what to do anymore. I care about my brother, I do, but I'm afraid that if he does live here with me long term, I'm afraid I'll start hurting myself again. I've been really trying to get better myself and work on my mental health, but my family has been making that extremely difficult. I'm ready to leave state and never talk to any of them again at this point... but what should I do?How can I help?

TL;DR: My brother has been addicted to drugs and I won't let him stay here anymore. How can you help someone that refuses help and won't go to rehab?

EDIT
A lot has happened since I made this post. He refused help, refused to take care of himself, ran away from where he was staying. All the usual stuff. But then something truly amazing happened.. My brother is finally turning his life around. He has a really good job and is saving up for his own apartment, and has been completely clean from all drugs and most alcohol too. I'm so proud of him, and I hope that he stays on this healthy path so he can live a happy, healthy life! Tough love actually helped. I know that isn't for everyone.. but when you have no other options, it may save someone.