Even if they were a huge fraction, you're considering one single axis. You're not considering population support or economic contributions by and on behalf of children, both of which are arguably much more significant than tax bill distribution.
The tax-funded support for “people in lower income brackets” are themselves very much slanted toward support for parents with children, largely because the American public is broadly fine with blaming poor adults for their condition, but somewhat less so for children in poverty.
Having benefited yourself, you shouldn't be bothered that others also benefit. It is only fair.
BTW, you can earn a 6-figure income and have negative taxes. The key is to have a double-digit family. This is what I do. Nothing is stopping you from doing likewise.
My tax bill sure indicates otherwise.
I decided at an early age not to have kids - at 12-13 I figured out that I was not suitable to be a father - one, I wanted the chain of crappy childhoods to stop with me, and two I have various conditions that I believe are largely genetic - I didn't want to pass those on.