Support bubble clarity - how many households is this?

[Snog]

Two people in a relationship, both live alone, bubbled together in a support bubble = one household, yes?

What happens when one of them has an elderly parent who lives alone. Can the elderly parent bubble with their adult child effectively making a household of 3?

No I think that is two households. You can only have one support bubble household.

Support bubble is a single person + another household.

You can't have a single person + another household + another household even if all single.

Aargh well that messes up my Xmas plans if it's two households