Multi-generational living

Sounds great! My friend has extended her house converting the garage to a small flat. Her sister has moved in. As neither has children they saw it as a good way to look out for each other and still have their own space. Good luck.

If all people want it, it can work really well.

D and GS live with us after relationship breakdown. I will really miss them when they move out.

I think it is a great idea, if you all get along. As Ellan says, and as there are no ulterior motives such as regular babysitting as you are 'on hand' so to speak.

If I was on my own I would seriously consider it.

Providing you all get along and also enjoy your own space from time to time and as long as there's no ulterior motive on either side i.e. babysitting when you don't feel up to it or someone at hand when/if you become infirm.
In other words not being too reliant on one another.
I remember my D saying that if she won the lotto she'd buy a large house and I'd suggested " with a granny flat " to which I could have bitten my tongue off as I personally wouldn't want her to be under an obligation as it's not my style and couldn't do that. Knowing full well she'd have agreed to it but I couldn't .
The arrangement is entirely up to yourselves.