when people say 'don't let them get to you'... to ask just how exactly?

Can you ask him what his problem is with you? It's not you it's him but if he can't tell you then you'll just have to it go.
I'm in a similar position altjough I'm sad about it but have had to let it go for my own well being and luckily I can avoid speaking to them for a majority of the time. It's all over a m8scommunication but has gone on too long now and until recently I didn't even know what it was about.

I'd say you need to avoid him. Dont ring him. A short text if you have to. Avoid any interactions. Does he ever initiate contact.

I'm reading the book about the "let them"
Theory by Mel Robbins. It's helping me not take on other people's shit and to care less. It is helping. A bit.

OP, I'm sorry you're going through this. You're very articulate and perceptive about the nature of your response, and the thoughts and feelings that come up for you, and that's massively in your favour as it will help you process new ways to handle this.

There's a life coaching model which I think is based on CBT, which might be useful. When I've used it, it's helped - i need to use it more!

It goes: circumstances trigger your thoughts. Thoughts drive your feelings. Your feelings drive your actions. Your actions shape your results.

So your model might go:

Circumstances: brother says something critical
Thoughts: I'm letting everyone down/this will haunt me forever
Feelings: fear, anxiety, doubt
Action: appease brother/change plans (what is the action?)
Result: you don't enjoy the event/you change what you had intended to do

The trick, which has to be learned, is to ignore the feeling but change the thought.

The feeling is what's causing you pain - that shock fear punch to the stomach- so it's natural to focus on that. But it won't change without the thought changing, as the feeling is really in response to your thoughts, not the circumstances themselves.

And the trick to changing the thought is to come up with a believable alternative. You won't be able to get the results without believing your thoughts, so replacing "I'm letting everyone down" with "everyone will love this" when your brother criticises isn't believable. But, thinking "he's being grumpy" might be easier to believe. Then your model becomes more like:

Circumstances: brother says something critical
Thoughts: he's being grumpy
Feelings: mild annoyance/compassion
Action: shrug, invite constructive input, move ahead with plan
Result: event goes ahead as planned

Sorry for length - this helps me when I remember to do it! Best if you actually write it down in a way that's true for you

He knows what he’s doing though, and it’s abusive. How do you know what goes on in someone else’s marriage? He might do it to you because he knows it bothers you and you won’t stand up for yourself, but either way, the most important thing is the knowledge that he’s a bully and his behaviour, although directed at you, has nothing to do with you. He’s far from perfect himself.

I’d take the mindset of feeling a bit sorry for him that he is clearly very unhappy in life to feel the need to go about dragging others down instead of addressing his own shortcomings. No human is perfect, and that very much includes him!!

Have a look at Mel Robbins and the Let Them theory. I've found her podcasts really helpful

But again @VUtterlyFedUP remember that you can’t control what he does, only your reaction to it. When he says or does these things, they are symptomatic of is own issues and they are meant to pull you down so that he can have power over you. As that sinks in over time, you will learn to ignore him.

So what if he uses things as a stick to beat you with? It’s not your responsibility to make everything perfect, you’re only one person, it’s impossible. Besides which, when dealing with people like him, nothing you do will ever be right anyway so even if you really tried, things will never be perfect because he will always find something to criticise. Just stop giving him the reaction he wants. Ignore him completely!

You don’t need to make everything your sole responsibility. He sounds abusive, who gives a shit what he thinks!? Abusers are lacking in areas themselves!

Or the way I see it is, just because one person finds you annoying not everybody will, because we’re all different and perceive personality differently. Would I want to associate with somebody who thought I was stupid and was rude enough to tell me, anyway? Nope! So they don’t matter a jot. What matters is the people that like/ love me and treat me respectfully. OP, you’re never going to control what your brother does. You can only learn to accept yourself, warts and all, and learn to control your reaction to things he says.

Someone once told me “Somebody else’s opinion of you isn’t fact” and it helps me a lot. Just because someone thinks I’m stupid/awful/irritating it doesn’t make it true and some arsehole who doesn’t wouldn’t piss on me if I was on fire most certainly doesn’t get to decide my character.

I also think OP that wanting something that isn’t gonna happen is bad for you. I’m sure your brother loves you in leave to because they’re family” way, but I know you want a more personal kind of love. But have a word with yourself that it won’t happen - the sooner you realise the sooner you can move on.

When you learn that other people’s behaviour is not about you, it’s a symptom of their own insecurity and powerlessness, nothing can get to you. As a pp said, you need to come from a mindset that you are in control of your reaction.

People can only upset you if you give them permission to. I don’t say this to victim blame, you can’t always help it if you are upset by something in the moment, but honestly, you’re upset because you have low self esteem and somewhere inside, you believe the things that are being said.

Take the power away from them by remembering that the only reason they’re saying it is to make themselves feel powerful because they feel powerless and unhappy. It’s liberating when you finally accept that.

I'm so glad you found such a good psychologist. Yes it does take longer than you think at first to get over such bad treatment and abuse. I'm so glad you're on the right path now.

Imagine in his head he had the thought that he was the success and you were the failure. He realises you are doing well and he isn't and jealousy kicks in. With his new partner telling him he's right and stoking it, the negativity grows. He believes he's right and nothing you do will change how he as another person feels.

Grieve who he was and the relationship it was. Expect him to be the person he now is. Expect him to not like you. Once you can grieve and accept, and probably go through some anger too as you did not want this situation, you'll move on.

I’m lucky I found an extremely kind very experienced psychologist to work with , I think that even though I’m far away from the people who caused me pain I will continue to need to work on the health of my mind for a long time to come as it had affected me physically as well. I have to be very aware at all times of how I’m feeling and make sure I don’t miss any sessions. It’s been hard but the main thing now that gives me so much happiness and security is knowing that I don’t have to be scared anymore in this moment or going forward. But I still need to work on a lot.

Try and have a few stock phrases to shut him down. As pandering to him isn't working, it's reinforcing that he has this power over you and showing him yoh care what he thinks. 'I was answering a question about arrangements not asking your opinion'. 'If you'd like to organise it so it's less 'weird' then that's absolutely fine with me'. 'Do you think that's a helpful comment? What are you trying to achieve by saying that?' Or simply 'ok. Anyway...' and completely ignore without reacting. All said in a completely neutral voice so you don't get accused of being over sensitive/ hysterical etc.

Being upset about someone treating you like this is completely normal

That's not what that means! You're misunderstanding it. It means grow a thicker skin and learn to ignore it

The weight analogy…

@Therapyhelped that sounds incredibly painful for you. Let's hope they are both driving each other mad right now. I am glad that therapy helped.

Yes because one thing affects the other. So using the weight and allergy if you were the fat sibling and he was the thin sibling then maybe he had more confidence, had a healthier relationship with a girlfriend, found it easy to sail through interviews etc. Then you lost weight which he might think he was glad about, but then you had your own great relationship, started to go up the career ladder because your confidence was boosted etc and he realised that everything he had had always been in comparison to what you had and now he is in the descendant and you are in the ascendant. Of course it might be just one of those things or it could be a knock on effect e.g. you lose weight, you gain more confidence, you get a better job, and you get a better house, and you get a new car… It might be the new car that triggers him!

I grew up with a narcissistic mother who abused me emotionally and then financially then finally physically. My sister was treated like a princess.

My mother cultivated a smear campaign and I was nearly sectioned as a teen on her description of made up behaviour. She was simply trying to make me look mentally unwell and unreliable so she could easily discredit me if I was ever brave enough to speak out. She lied to family and friends to isolate me and make sure I had no support and that nobody liked me. If I reacted she used it against me if I didn’t react in the hope she would get bored she got worse and did more . I couldn’t win.

My sister soon joined in with the campaign and it became a game to them I think to try and sabotage every area of my life after I’d left home. It carried on for years and years. Going NC didn’t help as they would still do all sorts of malicious things to sabotage my work, relationships, my children .

In the end I gave up and decided to move miles and miles away and changed my name and changed profession. It was the only way a clean break and the only way to have any peace in my life.