I think that the only fair way is be to radically reform the system. It is insane that people who work full-time should still be unable to pay for a roof over their heads and support their children. I think the vast majority of people would much prefer to earn their own money and not be humiliated by having to claim benefits, but the system works against them.
I would like to see child benefit made universal and not means-tested (as it used to be), all children given free school meals and childcare to be subsidised or free. I would also like to see rent controls and nationalised energy so people have spare money and an incentive to aim for a better life. That way, parents could work, and pay taxes which would circulate in the economy instead of being diverted to the pockets of landlords and low-paying employers. If employers 'can't afford' to pay decent wages they could be given loans to tide them over, and pay the money back when things improve, but they should not be subsidised by taxpayers, and taxpayers shouldn't be paying mortgages for landlords either. If interest rates rise to the point that landlords 'can't afford' to pay the mortgage with fair rents, then councils could buy the properties and take over the rentals.
Those who work should be better off than those who don't, regardless of the number of children. I fully understand people resenting seeing non-workers getting paid to have children that workers can't afford, and those who work full-time being annoyed when part-timers get their money made up by the State; but when rents are ridiculously high, wages are low and basics such as energy eat into family budgets, I can see how hopeless it must be for many people.
It needs to stop, but doing so will be like unravelling a tangled ball of wool. If something's not done though, the likes of Reform will continue to gain supporters, and heaven help us all.