You made an assumption that her boyfriend’s family have a business.. and I disagree with you. Money IS just about cash, not hierarchy. My db may have no money but he’s every bit as important in the family.
Hmmm, still very defensive OP.
You wrote this: Dd is about to get engaged to her boyfriend of 5 years who, as an only child will inherit a multi million empire,
Whether or not it's a business is beside the point. And yes, you ARE planning to advise your mother to disinherit your daughter. You wrote this:
My brother needs money desperately whereas I don’t, so I have told her to leave everything to him, but am now thinking I should tell her to leave at least some of my share to my ds, her grandson?
So you are planning to advise your mother to leave money to her son and grandson, but omit her granddaughter. That's disinheritance, as far as I can see. And you are speaking for her in a way that allows you to claim the moral high ground at no cost.
Those of us talking about the symbolic value of money/wills/estates in families are NOT equating money with love. That's a crude and crass assumption. But I've seen enough of money in families (if you're born into money, one does see these things differently, perhaps) to know that, as a PP said really wisely above, a parent's will is their last act of care for their descendants. It doesn't matter whether that will is about £1000 or several millions of pounds or the dog. It's what that symbolises about position in the family, recognition, care.
I can't help wondering whether there's some guilt here or something? Your motivations & thinking are quite odd. You seem unconsciously patriarchal: you don't need the money (you married money?) and your daughter doesn't "need" the money as she's "marrying well", but the two men in your mother's life - son and grandson, do? Because, of course, Heaven forfend that the women in your family are richer than the men ...
And you won't disclose why your brother can't provide for himself, to the extent that he needs ALL his mother's estate.