Please see the following information from the Gov.uk website regarding childcare bubbles. Please pay attention to the first paragraph and the last sentence - you can only have ONE childcare bubble.
What a childcare bubble is
A childcare bubble is where one household links with one other household to provide informal childcare to anyone under 14. All adults in both households must agree to this arrangement. ‘Informal’ childcare means it is unpaid and unregistered.
Members of either household can provide childcare in a home or public place. This includes overnight care.
You can only have one childcare bubble with one other household. This means no household should be part of more than one childcare bubble.