It's hard to collect specific data on how many single-child families there are at any given time; a woman can declare on a survey that she doesn't want any more children. And then, lo and behold, there's another baby in the bassinet.
But according to the 2010 census, one in five women ages 40 to 44, (those at the end of their childbearing years), had one child, (18.5 percent), a share that doubled since the '70s.
By the same token, single-child families have mounted in Germany and Great Britain - not to mention China, where laws restrict couples to one child. The reasons are many: older parents conceiving later in life, a weak economy, child care challenges.
Lisa Barnes, Schuyler's mom, said their family plan was always to have more children. But when Barnes' mother died suddenly when Schuyler was about 4, life shifted.
"My mom was Katie's primary babysitter," said Barnes, 47, and a professor at Delaware County Community College. "We had to find new child care, and that kind of changed the way we felt about having more kids."
"We fell into a new life with just Katie," added Peter Schuyler, 52, a consultant in the solar energy industry. "And it felt good."
Lauren Sandler, 38, an only child, is the author of the just-released book, One and Only: The Freedom of Having an Only Child and the Joy of Being One, after spending three years traveling the country, speaking with psychologists, sociologists, and singletons and their parents, exploring the only-child phenomenon.
The Brooklyn mom and her husband, Justin Lane, 40, are raising 5-year-old Dahlia in a duplex that they co-own with friends, an arrangement that Sandler thinks may catch on, as more singletons are reared.
Sandler notes that people like Schuyler's parents are hard-pressed in our society to find adequate child care. "If we compare ourselves to other countries, especially other Western nations, America has done such a lousy job of providing social services," she said.
She said another reason for the uptick in onlies has been the recent recession. "When the economy declines, so does fertility. In fact, one-child families spiked during the Great Depression," said Sandler.
The theme of the single-child family is even being portrayed in pop culture. In Zillow's latest TV commercial, a modern family hunts not just for the perfect house, but a great place for lives to grow anew for their team of three.
As social pressures have eased, more women, especially among the highly educated, are delaying childbirth. However, the likelihood of a successful pregnancy decreases with age; some hoping to have more than one child never will.
After years of trying to get pregnant, stay-at-home mom Lisa Taddei, 37, of Wynnewood, gave birth to Hayden 19 months ago. She and her husband, Dave, 42, a business owner, definitely notice that more neighborhood friends and acquaintances in their play groups having one child.
"Because there will be more kids that Hayden will know who are only children, I don't think he'll be missing out on not having siblings," said Taddei.
Raising her 17-year-old daughter Rachel Steinmetz as an only child is certainly less unusual than when Kate Coady, 55, was raised as an only in the '60s, especially attending Catholic schools, where big families were the norm. And like many adult onlies, Coady has remained close to several childhood friends, who are surrogate aunts to her daughter.
But there's a fear of loneliness for Steinmetz when Coady is gone that sometimes nags at her.
"My dad died a couple of years ago. That was hard, without having any brothers or sisters," said Coady, of the city's Mayfair section, a client associate at Wells Fargo. "When my mom is gone, it will just be me."
Having kids is priceless, for sure - but most would agree that they arrive bearing large price tags. The U.S. Department of Agriculture states that a child born in 2011 will cost $235,000 to raise to age 18. And, families in the urban Northeast have the highest child-rearing expenses.
Economics are helping to dictate whether Fishtown resident Lauren Wrobel, 32, will be raising 15-month-old Bailey Grace as an only child. She and her husband, Matthew, 32, a marketing director, are part of the newest generation of city parents, parking Stokke strollers alongside swank cafés.
"We love our house, and we really want to stay in the city. But, it all costs a lot . . . activities, day-care, schools," said Wrobel, the general manager at Center City's Nest, a kid play space and emporium.
Studies suggest that onlies' achievements are at times higher than those of kids with siblings, especially in academics. But in studies covering traits such cooperativeness, emotional stability, and popularity, singletons are just like children in larger families.
Take Victoria Shaara. She says that when people meet her - parents of her friends, teachers, or other students on the campus of Pennsylvania State University, where she'll be a senior - they just assume she comes from a family with other kids.
Her mother, Robin, 48, herself an only, enjoyed it so much that she knew before she married she'd have only one child.
"Growing up, I could talk to adults easily and hang out at the grown-up table," said Victoria, 21, of Riverton, which is fairly typical of only children who find themselves immersed in adult-oriented settings from an early age.
Yet, for all the attributes confirmed by decades of research, only 3 percent of Americans believe that having one child is ideal, compared with 46 percent who think two is best, as revealed in a 2009 Pew Research Center survey of 1,003 adults.
Furthermore, Susan Newman, a social psychologist in Metuchen, N.J., believes the myth of the only child as a spoiled, bossy misfit still prevails. Those criticisms were initially suggested in the 1890s when G. Stanley Hall, the first president of the American Psychological Association, pronounced being an only child "a disease in itself."
Newman was over 35 when she had her son, Andrew, now 30. She said that she and her husband decided "not to press their luck" for another child when he was born healthy. Since then, she's been studying singletons and has written two books: Parenting an Only Child: The Joys and Challenges of Raising Your One and Only, and The Case for the Only Child: Your Essential Guide.
"There is so much data showing that only children are no different than anyone else," said Newman.
Ask any parent. Getting kids to the legal age to vote, and then some, is fraught with pitfalls. Newman said that just as parents of kids with sibs might face issues like favoritism and fighting, parents of onlies should steer clear of babying and pampering.
"The few problems in parenting one child tend to be no more than what parents encounter when raising two children," said Newman. "A lot of the success of raising any child really depends on how the parents do it."