Family Allowance started in 1945, and was not paid for the eldest child, only the second child onwards.
The latest ONS figures www.gov.uk/government/statistics/households-below-average-income-for-financial-years-ending-1995-to-2022/households-below-average-income-an-analysis-of-the-uk-income-distribution-fye-1995-to-fye-2022#long-term-trends-data-prior-to-fye-1995-are-not-national-statistics show that the bottom 10% of families with 2 children have incomes from all sources, including benfits of under £20,450. That is under £20,450, not of £20,450. So some will have incomes well below that amount.
In 2022 average rents for a family house, from government staitics was around £800, far more in London, www.ons.gov.uk/peoplepopulationandcommunity/housing/bulletins/privaterentalmarketsummarystatisticsinengland/april2021tomarch2022. However the rapid rise in private rents over the last year suggest that this figure has risen and thatt average UK rents are now over £1,000 a month, in London, over £2,500, www.theguardian.com/money/2023/apr/28/average-monthly-rents-hit-2500-in-london-and-1190-for-rest-of-uk, average energy bills for a 4-5 person household are around £3,500 a year - and poorer families live in the worst housing with poorest insulation standards.www.britishgas.co.uk/energy/guides/average-bill.html.
This means that for the average family in a rental property, and low income families are invariably in rental property, it will cost them £15,500 just for rent and energy.
If they are on the maximum income of the bottom 10%, £20,450, After rent and energy bills, (£12,000 + £3.500) they will have £5,000 a year, less than £100 a week to cover everything else, including food for a family of 4, not to mention clothing, working costs (travel and clothing), Council tax, even if on CTB, you pays some council tax.
For those households on incomes below £20, 450, the situation will be even more dire.
Perhaps, Primrose or others with her view can suggest a secure food budget and menu plan for a household trying to feed 4 people on, say, £50 a week, while assuming that the cooking skills, dietary tastes and time available for food shopping are the average for all households in the UK.
I have carefully given sources for all my figures, so that there can be no query about soundness of my sources.