aibu to say no?

This is also a way of shifting blame and guilt over his situation onto you... So all the 70 year old family members get off his case and focus their attention on getting you to toe the line and become another resource and enabler for the addict and their behaviour, rather than focus on what needs to be done by the addicted person themselves (eg do the work, engage with the methadone program, find a rehab program)

Be prepared for 'family help family', 'I would do it for you if the situation was reversed'
'no wonder I have problems when no one helps me, ' and the lifelong refrain of 'I wouldn't be addicted if x had just let me detox in her house that one time '
All of this is unknowable bullishit.

You can still be a support for this person, helping them engage with rehab and as a family member, but not by burning up your own life.

You can tell them from me that it’s absolutely disgusting to ask this of you and they ought to be ashamed! I’m so sorry you have been cursed with such an awful family. You sound lovely, stay strong and don’t let them drag you down xxx

OMG do not allow him to move in with you.
I have limited experience in that a family member went through something similar. He was smashing through patio doors in the night to get out to go try find more drugs despite wanting to come off it and not being fully addicted.
He needs to find help elsewhere to come off the drugs. Although this is incredible incredibly hard and we weren’t able to get any help so paid for private rehab.

Do not let him in your house OP, under any circumstances.

It’s not possible because if it was that easy then he could say with the 70 year olds. He has access to drs at the methadone clinic. He should talk to them.

‘He sells his methadone’ tells me he is unlikely ready for detox.
Especially unmanaged detox in someone’s house. He’s living in cloud cuckoo land as are your relatives.
also, getting off heroin doesn’t automatically make them a better person or become a pillar of the community.
its a true source of distress for loved ones when they discover that all the things they blamed on heroin still exist without the drugs.
true rehabilitation is a massive undertaking, overhaul and drastic life changes. It doesn’t come easy and only truly works for a comparatively very small number of people who can be amazing advocates and mentors for others affected by addiction

No.

if he wants to get off he should get a rehab referral. Absolutely no way when you live alone. I wouldn’t unless there were two big burly men and in the house 24/7.

all it takes is you popping out and coming back to some scary characters and being intimated in your own home. Or god knows what else.

YANBU. If he is being prescribed methadone then he has contact with professional services already. Is he engaging with recovery programme or peer support like NA? Is he in discussions about rehab or other interventions like subutex? You are right, he is still comtemplating change and not actioning the help that is available. It's incredibly hard to get out of addiction and as PP have said, professional help is what is needed here

He needs to do withdrawal under medical supervision. Absolutely no for both your sakes.

Don’t even think about it. There are reasons why people go into programs and rehab to get off that stuff.

He already has his methadone supplied. If he stopped selling it and buying heroin, he could stabilise on the methadone for a time, and then look into programs and detoxes and what rehabs and support are available to tailor down his methadone dose and get off the 'done.

That’s what I thought. Specifically the toilet scene. That was such a good movie. But so gross.

He can detox in a detox facility.

He is meant to be on the methadone program but can’t be trusted to follow through with even that.

In my country you have to take each dose of liquid methadone at a pharmacy. I know this because I was picking up a script when all the heroin users were getting dosed on methadone.

There are clinics that your brother can go to to safely detox from methadone. There are drugs they can give him while he detoxes in a safe place. There’s literally a protocol.

He wants access to your flat to steal from you. Also, stealing from you will be preferable to him withdrawing in your home - screaming, sweating and shitting everywhere - because that is what happens. Heroin makes people severely constipated. When he’s coming off it it will be very messy.

Hope your mind is made up by now!
As a pp has said, three or even four days isn't going to get him straight, for good.
He needs supervised care, where there are people experienced in dealing with withdrawals of various types.
Often, other temporary meds are employed by a prescribing doctor. A ‘civilian’ with no experience of either the use or the discontinuation of serious drugs won’t be sufficient to get him through it.
Sure, he can try the famed cold turkey route and be as sick as a dog for days, distressing you and desecrating your home, but its far more likely in that case that he'd find a way to get out and score again. (Any Valium or even Nurofen Plus in your house would be gone in a flash!)
All said, it’s a ridiculous and careless proposition from your family, and you must feel no guilt in refusing.
It’s a job for the medical profession. Stand firm.

No not if you don't want to be relieved of possessions etc.addicts are akin to predators always looking for an opportunity.
As pp have said a couple of days isn't going to do a thing and it wouldn't be a couple of days once moved in he'd milk that situation for all it's worth.

No. Its absolutely not safe for both of you and will fail. He knows it too thats why he is keen on this idea.

Watch Trainspoting.

Even if you can't convince your family that it's a bad idea, you still have the power to say no. Only you can let him into your home. There is a lot of pressure, but you can say no. They have no power over you.

Absolutely not. Please don't do this.

He might die. He might kill you. He needs professional help.

Absolutely not. YANBU ! That is a horrendous position to put you in. I knew users (in a past life - was not tempted !) One 'friend' took advantage of everyone who tolerated his behaviour and stole the rent money from the mantelpiece of the mutual friend (non user) he was staying with. He never changed despite all the protestations that he would. He died of an overdose. You are very vulnerable if you put yourself in this position and it is NOT your responsibility....stay strong OP.

There is no way I would agree to this. The whole idea is mad. He needs professional support.

You would be putting yourself at risk if you allowed him to stay.

No, you can’t manage someone coming off heroin. It’s a job for a professional and, that aside, having a heroin user in your place (with potentially, other users or dealers turning up) is absolutely to be avoided.

No No No and No.

You ever seen anyone in withdrawal???
Don't do it OP.

No. No No. Absolutely not.