A big family bill need not wipe out your safety net. Set up separate savings...

https://www.toddleabout.co.uk/parenting/planning-for-big-family-costs-without-losing-your-financial-buffer/

A big family bill need not wipe out your safety net. Set up separate savings pots for the cost and emergencies, then test your plan against an awkward month with a repair, higher bills or less pay. You’ll see what you can truly afford before you commit.