It's definitely not true that both parents need to work. I know many families where only one parent has an income, and it is a very low income (one works as a mover for example) and they manage to eat and live etc.

Do they live upper middle class on this income? No. But they do live and have multiple children.

And I can guarantee they’re on government assistance because I know what a “mover” makes, and I know what diapers and formula cost, and they aren’t paying for multiple children on that salary alone.