Is the AIBU that your don't think people should spend their own money, that they have earned, on themselves while they are still alive?
Even before the update, it was clearly the fact that they hadn't earned the bulk of the money themselves.
I was also wondering that happened to the daughters and younger sons - or did each just have one son and no other children? Also, is it definitely true that the business was struggling, or did they just see their opportunity to 'cash out', give up working and happily live a privileged life off the back of the previous generations' hard work, whilst barking at the younger generation about how disgraceful it is to happily live a privileged life off the back of the previous generations' hard work? Maybe they saw it that the business represented ongoing family wealth and, in selling it and taking the proceeds, that made it their money alone and broke any claim on it from others.
That said, they are shameless hypocrites - they seem to think that they are deserving but nobody else. It reminds me of (among other things) university tuition fees, when they were first brought in - when the (mostly university-educated) politicians were spluttering indignantly that university was a tremendous privilege and how dare students expect the ordinary, often low-paid, taxpayer to fund their education that would enable them to end up in a well-paid job.
It also irritates me intensely when smug billionaires will proclaim that they don't want to leave their money to their children, as they need to learn to make their own way in life. If you end up with a few millions, it may well be a direct result of your own effort, hard work, sacrifice and risk taking; but nobody can ever work to actually earn or deserve billions: you might have worked hard, made a few wise decisions and/or got lucky and then it all effectively just fell into your lap by default by some quirk.
They can't have it both ways, though: gratefully taking what was handed to them on a plate and then complaining about others who would like (not even necessarily expect) exactly the same as they had.
I agree with PP about immigrants, too. So many people are blue in the face about 'these people' wanting to come and take, when all that they (like me) 'did' to get to the UK/other wealthy country was to happen to be born here to parents who happened to be born here and so on. Either that, or they were immigrants (or the children of immigrants) themselves!
It's the easiest thing in the world to tell everybody that we should all be happy with our lot in life, when your lot just so happens to have been the (comparative) equivalent winning the jackpot in a lottery.