It's here.

[Joe Black]

What happens when the parents are still alive but the kids get married etc. Does everyone still stay in the one house, or do the kids move out, buy another house which is then 'in-debted' to their kids, while they have to pay off the old folks one?

Starts to sound like the beginings of a pyramid scheme to me.

[BlasterBates]

Does this apply to sperm donors ?

[Joe Black]

Possibly...

here's one I built earlier:



The upper floor is of course obviously the most expensive.