My grandparents want to include me in their will. My mother is furious.

Let your grandparents do what they want. Suggest your mum isn't executor and they use a solicitor as executor.

I think you need to keep repeating this, ad nausem. To your grandparents and your mother.
It's absolutely their right to leave something to you if they wish to.
Make sure you remember how compus mentus they are right now, as your mother could well try to contest the will down the line and say that they were incapable and/or that you coerced them. Have your ducks lined up and cover your own back.

It is nothing to do with her.

70/30 in whose favour?

Let them sort it. Your mum is the one being unreasonable, she’s not entitled to their money. They can very well choose what to do with it.

It's your grandparents money, so your mum has no right to give them grief about their choices.

I would suggest to them that she is not the executor of their will, though. Or at least not the sole executor. I doubt that she can be trusted (though I wouldn't put it that way). As I'm discovering, being an executor can be a total, stressful nightmare, so if they're determined to have her, put it that they should have a second executor outside the family to 'help ' her.

Are you saying they ask for advice about their wills? I think that maybe you should explain to them that this might mean that the wills could be contested on the grounds that you influenced them. I don't think you should express any opinion and not discuss it with your mother either.

My parents are leaving everything to their grandchildren, and nothing to my sister and I. They say this is to avoid two lots of inheritance tax. I see the logic, and I’m glad my kids and my sisters kids will have a financial leg up. I am a bit hurt but wouldn’t dream of commenting or interfering. Your mother has no right to make a fuss.

I think it depends of the total sum of money involved and the percentage you're going to get. It's normal to leave to the next of kin (your DM) and in turn your DM would leave to you.
Are the amounts involved worth 'fighting' over? At the end of the day your DGP's can do what they want.

Why are they calling you for advice? They should seek legal advice.

Wonder if your mother was counting on her inheritance to help her out in her old age. So many women of this age have inadequate pensions . She could also be thinking that any care will be up to her. Have you asked her what her objections are ?

But you don't say if it's a majority share to you, or a small part. I think that makes a difference.

I think if it's your dm doing all the looking after them, it's a kick in the teeth tbh. My dm makes noises about leaving it all go the gc. The gc have to be forced to visit her. Openly say they can't stand her. They do absolutely nothing to help with her shopping, cleaning, medical appointments, rehab, days out, holidays, gardening, resolving scams, taking back things she's bought in error. The list is endless. If you're a gc who does all that and your dm diesn't fair enough. Otherwise, it's ungrateful.

It’s down to your grandparents. That said I wouldn’t want a relationship if my mother behaved like that.

Similar thing happened in our family. Quarter of a large ish estate went to the grandchildren (including me). Out of the family only my DF was not happy about it….. stay out of any discussions with any of them if I was you . Let your generous GPs speak to a solicitor and have it drawn up properly.

Sounds like you're all getting or got better deals than I will! 😅 I'd tell your mother that she should think herself bloody lucky, OP!

Do not discuss it with anyone, OP.
The only mistake your grandparents are making is chatting about who should get what. Ideally, they make their Wills, and nobody knows anything until after the death(s).
But, ultimately, none of us has any right to inherit anything (if we're in England).

My GM did it as percentages. Us 5 grandchildren got 10% each, her child then got 50%. Your grandparents should do whatever they want to do with their money. But your mum sounds awful.

Tell them to go and get their will organised, it can stay private until the time comes to read it, by then they will have sadly died and your mum can huff and puff all she likes it will be a legal binding document.

It is perfectly normal for grandparents to include grandchildren in their will. This is your mother's issue keep out of the dispute and accept your inheritance whenever that is given. Hugs

Grandparents should know their DD well enough to have avoided telling her about it.

Tell them you appreciate it so much and that they should will their assets as they choose.

I am guessing it’s not news to you what a nasty piece of work your mother is?

Surely that’s perfectly normal? My parents made a modest (10k each) bequest to their 6 grandchildren. Their children received the bulk of the estate. Why on earth would that be unreasonable?

It's their choice. 🤷‍♀️ I know that my parents are splitting their will equally among DB, my three DC and myself, so I'll get a fifth. That's just how it is. I agree with pp to leave your mother and her parents to argue it out themselves.

It's your grandparents will and their choice as to who will benefit. You should not turn down their generosity, your mother will just have to accept it.