How do I make peace with this?

I don't think this is about how much your mum loves you, but rather that she holds extremely old fashioned, traditional, views about the roles of men and women in society. Males inherited family wealth, when a female married she became the responsibility of her husband, who provided for her. The female was traditionally the one who took on the caring role in the family, too.
The big issue is how to persuade your mother, and your brothers, that society and attitudes have radically changed so that society is fairer now. She needs to understand this in order to be fair to you.

@ForeverWeBlend I agree with this. Judge people by their actions.

As people often say on MN - she is showing you clearly who she is. You should believue her.

Your mum wanted to make the point that her 2 favourite children are the boys. You are not their equal and she wants you to know that. It's probably always been the case.
My mum is the same. My younger brother can do no wrong. I can do no right, despite being the one who over the years had done almost all the caring & support. In her mind I am lower status than her because I am a younger woman, whereas my brother is higher status to her because he is male.

I'm now LC with her to keep myself at a safe emotional distance.

why should you do it for free to ensure they get more?
essentially that would be whats going on, OP is expected to sacrifice her time and work for free so that her brother's inheritances can be preserved. She is treated like a slave while they are treated like royalty!

I’d stop running around and taking care of her, she’s made her feelings clear and unfortunately she doesn’t think you’re worth much at all.

She has made her feelings clear. You get nothing because, to her, you are worth nothing. Your drug addict brother is worth more, in her eyes, than you. Her actions are not those of a loving mother. She is a cold callous bitch to do this to her own daughter. My view would be fuck her.

I would be distancing myself with a view to go non contact. I would absolutely not be doing any caring for her. Let her use your brothers inheritance to pay for caring fees, why should you do it for free to ensure they get more?

Would you do this to one of your children? What kind of parent disinherits their daughter in favour of a drug addict? Walk away, she’s made her bed so let her lie in it.

No idea if you're in the same position.
If so don't let take up headspace.
I do remember DM saying she'd be making me executor....
although someone did say when the time comes it's not a given and I didn't have to deal with it all.
Whether I'd be left anything or not I did tell both parents it's a job I could well do without so wouldn't be doing it anyway.

Extremely dodgy plan by your friend there, she could find herself personally liable for the money she cheats a will beneficiary out of. Seriously, however unfair it is, she should not do that, she should just tell her friend that she's not willing to be the executor of such an unfair will.

You can't make peace with this. It's really appalling of her and of course you are upset.

I would distance yourself and see her much less often - also stop providing care. She can well afford carers.

Write all your feelings down, thinking them all through, then go to your Mum’s and read it to her. Once done tell her that you need some space as you’re finding the whole situation very painful and then don’t see her for a few weeks. A period of separation may help you to gather your thoughts and also your Mum may finally come to realise the devastating impact her decision is having on her daughter.

I've found reading this very upsetting. I'm no contact with my mother, been three months. She sided with my sibling over her very out-of-order behavior that was obvious to a blind man and then 'disowned' me when I called it out. It hurts like hell but wild horses wouldn't drag me to see her without an absolute retraction and apology. I can't see how you can make peace with it while your mother maintains her position. It's deeply wrong and dreadfully unfair. It's also tantamount to her admission she failed in bringing her sons up adequately and that they are not as stable and sensible as you. So perhaps she sees it as guilt money. But it punishes you for her failure. I'm with others, protect your heart and withdraw. A letter is a good idea, be as honest as possible about how it's made you feel and that your healthy boundries mean you won't prostrate yourself for someone who clearly doesn't value you. I really feel for you.

Well, she's made her will bed...
I guess most of her assets will now have to pay for any home helps or carers she may need, also any residential care she will need in the future.

@MissingYellowzigzags I'd be like you. Her actions have put your entire relationship in a blender. You need to take a really big step back and prioritise your DH and kids - you've nothing to lose anyway - and let your brothers step-up.

💐

She'll have to spend a lot of that money on care won't she? Please tell me you're not really going to wipe her bum after she's treated you like this? Let your brothers know she's going to need to pay for a carer and see what they say then.

Your mother has got you dangling on a string hasn't she? She doesn't love you, you are just the scapegoat.
Well I wouldn't let her behave like such a fucking nasty bitch with me.
I would write her a letter setting out exactly why she is being so unfair and would then go totally no contact and tell her that you will only reconsider if she changes her mind and splits her estate equally between the three of you as this is the only way you can accept that she cares for you all equally.
I would also tell her that I will not be providing any care either now or in the future and she will need to arrange for paid care if your siblings won't step up.
You say up thread that you love your mother so much. How? How can you love someone who quite obviously doesn't even like you.
I am a lot wealthier than both my siblings but my parents are dividing their small estates equally between us. I would cut contact if they did otherwise.

I'm encouraging DH to talk to his parents about their will in plenty of time. We expect there might be something similar afoot. Best to know now as we will step back. If BIL is getting all the money then he can earn it (or lose it as PIL will have to buy in care if he doesn't step up).

Doesn't pointing out that it affects your dc and means they will ultimately been treated unfairly compared to their cousins make any difference, OP? Even if they are each directly left an equal share, what's left for them to benefit from indirectly via their parents won't be equal. That money could help them in significant ways either while you yourself are around or potentially after you are gone.

It’s too much to expect from yourself that tog ‘can make peace’ with this or continue to do the care grunt work. I would be remove myself from all caring duties and go low contact.

I would let my mother and siblings know given the circumstances it’s now for them to arrange her future care, that your well being also matters, indeed it is your first priority. I really wouldn’t take another call from any of them for the foreseeable.

Organise a professional counsellor and talk this out with them extensively. Spend some time with friends and tell them how heartbroken you are, the need for support etc.
Consider what you can do to feel better. It is her choice but one she is making knowingly and that is very hurtful.

Acceptance may or may not come in time, but you owe it yourself to take care of yourself - your feelings and the best way to do that is to take a huge step back and at least stop her taking further advantage of you. It is never ever okay to treat children differently and sowing the seeds of generations of division, sadness and rivalry is a terrible legacy to leave behind, but that is her choice. I imagine she wasn’t much of a parent to you in the first place and therapy would be a good idea.

Look after you

It’s my opinion that the only way of writing your will, is to split any inheritance equally between your children. There’s nothing else to do.

My heart goes out to you @MissingYellowzigzags . I would walk away and go absolute no contact with your mother.

I’m so sorry! This is awful.
I’m in your position care wise. I have 2 other siblings but it’s me who does all care for DM, 90yrs. I’m also in a better financial position than my siblings as DH is a high earner.
However Mum has made a will, small amounts to grandchildren and the rest divided equally between us.
I cannot understand how your Mum thinks, my parents were always fair. In fact, my Mum is always saying that she’d like to give me more as I do so much more for her!
I’m not sure I could come back from your position. I’m very close to Mum and the hurt would finish me off like a knife through the heart. I would certainly cut the care and become low contact, that applies to your siblings as well. How can they all think like that?
I would have to explain about the injustice, again, it’s not about the money, but being treated and valued the same.
You cannot rely on your siblings to share their inheritance. Indeed, through my work I’ve seen many reasonable people turn into selfish gits when money is involved.
💐

I agree,
they see the daughter (or whomever is the designated blacksheep/scapegoat) as inferior, her subordinate status means that
1-she is not deserving of the family wealth
and
2-because she is a subordinate she relegated to the menial tasks of serving the needs of the higher ups (the parent)

How do you make peace with this?

You don't. You can't. It's so unfair that it cannot be made peace with, some things can't.

Did your mum inherit from your dad? Did he die intestate? If he did, then you have a legal claim to some of the estate and if I were you I'd tell your mum you'd be contesting her will on the grounds of your dad having wanted you to have some money.

I also wouldn't be planning to do her care in her old age.

@Crumpleton
It sounds as if you've come to terms with it which is a good thing....

Thanks for your reply

I wish there was an easy answer OP but I really can’t see one, you seem to have such a lovely relationship with your Mum that it’s hard to understand how she thinks this is right in any way at all.
The way I see it is, if you continue as you are with her, she will think you have just accepted what she has has done, and I really think she needs to realise how much it has hurt you. I would certainly put her right about your husbands pay, even though I think overall that is of no consequence. Point out to her that she is only 75 and could live for 20+ years yet, why hasn’t she stopped to think that anything could happen in that time, your personal finances could change overnight at any time, no one knows the future.
I think she’s being outrageously unfair and even though it will hurt you I think that you should step back from your relationship with her, tell her exactly how hurt are, explain how ridiculously unfair she is being by not taking a long term view. Leave her to think very long and hard about the choices she has made. And as for your two brothers not immediately fighting your corner they should be ashamed of themselves.
I wish you the very best of luck and hope things can be turned around for you.

i think there is an unspoken expectation that I will do the care
If I was in OP's shoes they'd not see me for dust if mother needed any assistance!