Recently there has been some discussion in the Presidential race about the taxation of parents vs. childless taxpayers. The discussion has been ongoing, but it was kicked up again when a 2021 video of J.D. Vance resurfaced where he said that taxpayers with children should be lower tax rates than those without children. There was some political back-and-forth about this idea, much of it tied up in the framing of the issue, with the usual bad faith on both sides about the fundamental issue (in short: most Democrats and a small but growing number of Republicans support increasing the size of the Child Tax Credit).
Let’s leave the politicking aside for a moment and focus on policy. As many pointed out in response to Vance’s idea, we already do this. In fact, we have almost always done this in the history of the US income tax — “this” meaning giving taxpayers at least some break for having kids. For most of the 20th century, this was done through personal exemptions which usually included some tax deduction for children, and later in the century the Child Tax Credit was added (after 2017, the exemptions were eliminated in favor of a large CTC). Other features of the tax code also make some accounting for the number of children, most notably the size of the Earned Income Credit.
The chart below is my attempt to show how the tax breaks for children have affected four sample taxpaying households. What I show here is sometimes called the “zero bracket” — that is, how much income you can earn without paying any federal income taxes. The four households are: a single person with no children, a married couple with no children, a single person with two children (“head of household”), and a married couple with two children. All dollar amounts are inflation-adjusted to current dollars

