To be devastated?

It's not a bad thing your brother is helping financially. Use the opportunity to focus your finances on your own security. Your brother might tire of supporting your son in which case you'll be back to chasing your tail. If he doesn't, you'll be in a better position. Eventually your son will grow up, pay his own bills and wonder how the hell you managed to keep everyone else afloat (or at least that's how I feel about my own parents).

Let him go - he needs to grow up and he's doing it. You sound aggrieved that he's grateful for the help he's getting from your brother. You sound angry that someone else is helping. Why not focus on your own health now that you've got a much needed breathing space?

Putting his autism aside ( may or may not be a factor ) young adults can be very self centred and selfish . Throw in a relative giving him a grand a month and of course he's going to keep that person on his side.
tell your son you will always have his back and you are glad he's finding his feet ( even though you know it's not because of anything he's doing independent ) and remind him you are only a call away .
Then learn to live your life for yourself.

It’s this thought process:

I feel cheated out of something I can never get back. I feel like I've lost something precious and now my brother has taken over, making me look incompetent and unreliable.

I understood he'd always flee the nest. I just didn't spend 18 years working myself into the ground for it to be like this.

Lets make this clear - your son owes you nothing. He didn’t ask to be born to you, you chose to have him.
your love and what you did SHOULD be unconditional.

Whereas you are smothering him and making out like he owes you, because you brought him up??

the very fact that you stated he should live with you, ‘like other Uni kids do’ is ridiculous. Give your head a wobble before you lose your son.

This. Acting like a martyr is not going to impress your son. If you were so ill you couldn't help him you should have told him that. And moving in with your partner to a smaller flat when you want your son to come home for a long summer holiday seems ill advised.

I know its easy for me to say this but don't be upset. I bought up my son alone and we were very close but after uni he really kicked off, refused to come home and started hanging out with his deadbeat father who didn't pay a penny for him or see him at all when he was growing up.
At one point I didn't even know where he was for a year.
He just wanted to be independent but was as yet still too young to know how communicate this properly.
I just let him get on with it. A couple of years later and we were as close as ever. Not surprisingly his father totally let him down.
It's a rite of passage they must go through.
Take this opportunity to sort out your own problems and let him get on with it.

OP this isn’t the culmination of motherhood. This is just one little step along the way.

You and your son have built deep deep roots. The majority of your lives will be with both of you as adults - this is just one step along the road, and yes it’s sad that it isn’t the ideal set up of him coming back to your lovely house in the holidays etc but you have had a really dreadful time over the past few years and you are still FIGHTING and recovering and building, and it takes time.

18 year olds are famously a bit self absorbed and yes it’s infuriating that your brother is suddenly mr magic fixit but hey, he is helping, and it’s nice from your son’s perspective. Take the help, bite your tongue and look after yourself. Build yourself up and don’t panic about the relationship with your son. It goes soooo deep. It’ll still be there. You have years and years ahead and start thinking about how you’ll both adjust to that relationship with you both as adults. That’s the next stage.

Why are you doing everything for him? Why are you sorting everything for him? Why are you constantly visiting at uni? You sound very very involved.
your brother is not stealing your son? Why aren’t you happy that he is helping your son?

I am going to go against the majority here and say you are absolutely not being unreasonable to feel the way you feel. It must feel like you're being discarded in favour of a richer person who has never given a fig for your DS. He is young and tactless. When I remember some of the things I said to my single mum when I was a young adult, I cringe.
However. You have an opportunity here! As pps have said, it's time to look after yourself now. Time to become happier and healthier-best of luck to you.

You know your brother can see you aren't well and is helping you out too with your son?

I think you need a doctor appointment

OP you've had a rotten few years. But you're right, you have fought and worked and done everything you can to support your son. I understand why it must be harder for you than for many to let him make steps towards living his own life - he still (presumably) finds things tougher than others due to his autism, his struggles with depression, it was the 2 of you together against the world.

But you've done the fighting and the raising and the upbringing. Now he has others he can lean on too. It's not just the 2 of you. He has his girlfriend and your brother is finally stepping up too. Yes it sucks that he's swanning in and taking the credit. But if it helps your son, then welcome it. He can have his relationship with his uncle separate to yours with your brother.

And let it take the pressure off you trying to find the bigger place while you and your partner are ill.

Let your son know you're there, will always be there, will always have a place for him to stay (even if that's a sofa) but let him stand on his own feet when he wants to (even if you see it as your brother propping him up). He'll come back, grow up, see what you've done for him. Your brother's doing a bit of a Disney dad role, but as kids grow up they see this.

I agree with pp's that travelling to clear his halls for him while you had pneumonia wasn't sensible. He's made it to uni, he has friends and a girlfriend, he could have done that himself, even if it was finding somewhere to store his things over the holidays. He's not 13. Be his backstop when he needs one.

Whatever you do, do not place the burden of your happiness on your son’s shoulders. That is emotionally manipulative and he will never forgive or forget that if you keep this up.

Your happiness is your responsibility. Forge a better life for yourself and let him get on with his life. Guilt-free.

You should congratulate yourself that you have raised a son who is independent and wants to fly the nest.

Be happy for him and please let him go and hide your pain. I cannot emphasise enough that it is not his job now to make you happy.

Sorry, but I think you have spoilt your son a bit by not teaching him to stand on his own two feet.

I think you need to use this time to focus on yourself: your mental health and finances. If they are in a bad position, you will bring your son down. He's your son but he is also your brothers nephew and if he is happy to help, let him! It doesn't replace you at all and your son needs the help and if he doesn't have a dad on his life, having that male figure is priceless. If you're in a one bed, it's unreasonable to expect your son to live there over the holidays.

This is a blessing in disguise. Cut the apron strings and build yourself up again with one less thing to worry about and and one less expense!

I get you are hurt. But remember that your brother can never replace you. You are his mum.

One thing I will say is that you need to let him go. Just like in relationships, having somebody be clingy towards you is always likely to have the opposite effect. The more you try on and hang on to your son, the more he will push back and find being with you draining and unappealing. Whether that’s fair or not.

Support him with a smile and let him enjoy life. Is he happy now? That’s what you need to value.

Teens can be ungrateful. But parenting is not transactional. My older teens have their off days too. I am firm with boundaries, show love but try not to smother them and whilst they do owe me a level of politeness and respect, they do not have to pay me back for all I have done for them.

The stuff with the brother is unfortunate but, basically, your son is right. He's an adult now, and has to live independently. No young man wants a parent who smothers, indulges and relies on him for their own happiness. Time for you and your partner to make a life for just the two of you.

I’m sorry OP, it sounds very hard.

Currently, you’re forcing yourself on him - at least that’s how he’s perceiving it. You can continue to force yourself on him, but it won’t bring him closer, it will only push him further and further away.

I think you have to find a bit of inner strength, and figure out a way to step back, give him some space - give him what he thinks he wants.

You know you will always be there for him. But you also must know that as he becomes an adult, he needs to move away and be his own independent person (his uncle is a means to and ends towards this). You knew this day had to come, sooner or later.

It inevitably feels much worse because of all that’s been going on, but also because of the co-dependent, intense ‘you and him against the world’ dynamic you’ve set up.

We all love our DC and would do anything for them. But as parents we also know that we’re raising them to ultimately go off and be their own person.

If you continue to force yourself on him, and stop him from being his own person, and/or guilt him into staying with you, you’re going to do a lot more harm to the relationship than if you let him go with good grace.

He’s young and he needs to do this. But if you handle this well, you’ll come out the other side, and go on to have a normal, loving adult relationship with him.

It will look different from the old relationship, but that’s OK. It has to be, because the alternative is no relationship at all.

I agree with this.

You can't force help on him now he's an adult, and you can't force him to live with you.

I'm sorry you're having such a shit time. But it sounds like you're pushing your son away by being so involved.

I think you're missing the point. You need to step back and allow your son to be an adult. Yes, your brother is 'taking over', but as others have said, he's not going to want to support your DS for the rest of his life. He'll get tired of it, especially if or when he has DC of his own to support. When that happens your DS will have to, as they said, 'shit or get off the pot'.

I know it's not easy to let go. I 'smother mothered' my younger son until he, himself, told me to 'back off'. He did it in a nice way, of course, but he was right and I was actually impeding his independence. My 'caring' was actually putting a weight on him because he felt he needed to do what I said instead of finding his own way. I was stifling him. Your son has used hurtful words, it's true. But maybe that was the only way he could 'break away' from you doing too much and his dependence on that.

Give it time and give him space. Keep your resentment to yourself and work on ridding yourself of it. Once the dust has settled you and your DS will be able to form a better, more 'independent' relationship.

Your son sounds awfully ungrateful and uncaring towards you. I'd distance myself based on that alone. He needs to apologise and start acting like a decent person, before throwing demands of you to magic up a house. What a spoilt brat.

The rest about him being "grown up" and shifting his problems to his uncle - I suspect soon will fall apart anyway, once the novelty for your brother wears off and once he's done showing you up. Bet your DB enjoys fixing things, whilst making you look incompetent and incapable.

Leave them to it, he will come running back I'm sure. Take some time for you and your partner.

It's a selfish age and if he's autistic, he's probably also a little less emotionally developed than his peers, This may be a slightly late but "healthy" and necessary time of him rebelling and becoming less dependent on you.

Honestly the best thing you can do is encourage him and develop your own life a bit more, continue being loving and supportive of course but back off.

It's annoying I'm sure seeing others seem to play super-parent, but in time this dynamic will probably fade or change. If it doesn't then the positive way to look at it is that he has some other supportive family members around.

Give him some time and take the time yourself to heal and focus on mending things in your world

It's not unusual for a college kid to not want to live at home for the Summer. I went working abroad and l am in my 60s.
My dc travelled and took jobs in university city etc so this is just part of older teen years. Let him off but keep a wide open door for him and keep in touch in a friendly non overpowering way. This is a time of change. It would be more worrying if he wanted to live with you forever.
And let his uncle help him. He needs a wider family. And you do need help. Maybe thank your brother and instead of being suspicious of him think:: at last someone is taking some of the burden.
You have done a good job. Take this time to chill and get on your feet.

@CryingMamma your username illustrates the core problem. Your suffering, and how all this is about you, what you've suffered, what you've sacrificed, how you sat on the floor eating pot noodles to help him, how your health is bad, how you did everything. I don't mean this in a bad way as I am sure you were wonderful so many times, and I salute you for that. But it's all part of being a parent, isn't it?

Your post seems to push a belief that now he has to pay you back, by sitting in a small flat all summer with you being constantly ill, struggling with bills, a new partner he doesn't know. He's 18 now, though, he has a life to live, he's flying the nest! He absolutely shouldn't have to stay with you. In fact the distance will be good for you both. Your life does sound very hectic and unsettling tbh.

Your brother might be a judgemental bastard which is horrible and that's on him. But he is really, really helping your son and that's amazing. That's not him replacing you as a parent. That's an uncle stepping up when he needs to, and that's great.

I think this might all be rooted in you feeling frightened that your losing your bond with your son, which is I am sure a common fear when kids grow up. But you WILL lose that bond if you suffocate him, and resent people who are helping him. I'd relax on the pushing him to live with you, concentrate on getting yourself in a better, calmer place, and then your relationship will naturally get stronger again.