Even the term itself feels tinged with melancholy, some undercurrent of not-quite-enoughness, but the various alternatives — “singletons,” “onelings,” “one-offspring” — never stuck, and so we are left to ponder the only child. And more American parents are pondering the only child, because more American parents are raising them: The proportion of mothers who had one child at the end of their childbearing years doubled from 11 percent in 1976 to 22 percent in 2015, according to Pew Research Center, and census data show the trend continuing to tick steadily upward.

Culturally, only-child families — the fastest-growing family unit in the United States — are in the midst of a sea change. Individually, only children are the same as they ever were, which is to say that they are most definitely not all the same, which has never stopped society from branding the cohort with a slew of profoundly unflattering and occasionally contradictory stereotypes. They are spoiled brats, troubled misfits, social aberrations; they’re attention-craving showboats, but also, somehow, reclusive weirdos.

But in recent decades, something has begun to shift. Families are shrinking, and improvements in gender equality have made childbearing more of a question than a given. As Gen X and millennial women prioritize personal and career goals, as couples marry and start their families later in life, more parents find themselves mulling the logistical, financial and philosophical possibilities of a smaller family: What would it mean for them if they had only one child? What would it mean for their offspring?