I'm not in that demographic, but I would want everything to go to my children.
As others have said, MIL has set it up so that her partner has the right to live in the house (it's her house, which she's owned since her 20s), but technically everything goes to dh and BIL. They have - oddly - gifted partner's son the garage, which was on a separate deed, so partner's son oddly has a ransom strip to the side of the garden, even though neither he nor partner have a claim to the house. I hope that it won't be an issue - partner is an absolute shit, but his son is okay enough - but it's added an unnecessary complication to the whole thing, which I hope will play out one day without any drama. It remains to be seen though.
I am NC with my family, but last I heard, my mum and her partner had set up their will so that everything goes to the other, and then distributed to children (3 of us) upon the death of the longest living one. Now I have no idea if this is still the case, but the distribution was meant to be 60% to me, 20% to each of partner's children. But we're all NC. Partner's children went NC first, so they are more hated than me 🙄hence the unequal distribution, but no telling what's happened in intervening years.
I do wonder though what happens in a marriage where assets have been left to all children, but then after one partner dies, can the other just change it without the (dead) partner's consent. My mum's partner is pretty bonkers (as well as a convicted abuser), so it wouldn't surprise me that if he outlived her, if the whole thing got left to some right wing conspiracy theorist or some other bonkers cause. I don't particularly care about any of it really, but I am technically named as the executor even though we are NC, so I have no idea how any of that would work. They don't have anyone else as driven them all away. But I am just genuinely curious, even though the thought of all of it makes me want to hide under a rock - because there will no doubt be so much drama.