Lots of People Don't Have Kids

Data on men's fertility is harder to come by than it is for women, but in 2019, the Census released its first report on the subject (using 2014 data).

About 15% of women aged 45-50 (as of 2018) and 24% of men aged 45-50 (as of 2014) have never had children and most likely never will.

Unsurprisingly, men who were married at some point are much more likely to have had children than men who have never married. Among men aged 45-49 who have ever married (84% of men that age), 14.9% have never had children, while 73.6% who have never married (16% of men that age) have never had children. Fathers that age who have never married, also have somewhat fewer children on average (2.24) than men who have ever married (2.35), although the disparity isn't huge.

This is a relatively recent development in historical terms.

Being a childfree American adult was considered unusual in the 1950s. However, the proportion of childfree adults in the population has increased significantly since then. A 2006 study by Abma and Martinez found that American women aged 35 to 44 who were voluntarily childless constituted 5% of all U.S. women in 1982, 8% in 1988, 9% in 1995 and 7% in 2002. [Ed. 17.5% of women were childless, not necessarily all voluntarily, in 2018.]

These women had the highest income, prior work experience and the lowest religiosity compared to other women. Research by sociologist Kristin Park revealed that childfree people tended to be better educated, to be professionals, to live in urban areas, to be less religious, and to have less conventional life choices.

From 2007 to 2011 the fertility rate in the U.S. declined 9%, the Pew Research Center reporting in 2010 that the birth rate was the lowest in U.S. history and that childlessness rose across all racial and ethnic groups to about 1 in 5 versus 1 in 10 in the 1970s[.]

From Wikipedia. 

Non-Hispanic White men have the fewest children (1.7), then Asian-American men (1.7), then Black men (2.2), with Hispanic men having the most children (2.3). Foreign born men have more children (2.2) on average than native born men (1.7).

By education, men with associate's degrees have the fewest children (1.6), then men with "some college" (1.7), then men with bachelor's degrees (1.7), then high school graduates (1.8), then graduate school graduates (1.9), while high school dropouts have the most children (2.2).

These figures are for men aged 45-50, however, which has the benefit of capturing nearly their full number of children per lifetime, but has the downside of being a lagging indicator. The number of children that less educated and less affluent people have per lifetime has fallen relative to more educated and more affluent people since this cohort of men had children.

Most fathers have children with only one woman, but it isn't terribly uncommon for a man who has multiple children to have children with more than one woman. About one in six men (17%) who have two or more biological children (and 14.6% of men who have any children) have children with more than one mother.

Most fathers live with all of their minor children, but it is not uncommon for a father to not live with some or all of their minor children. Of fathers who have children under the age of eighteen, 72.6% of them live with all of their minor children, 7.2% live with some of their minor children, and 20.2% do not live with any of their minor children.

While most father's have biological children, 3.4% of fathers have only adopted children. About 2.4% of fathers are single father's to minor children. And 39% of fathers are also grandfathers.