Pete Buttigieg faced criticism from certain conservatives for taking paternity leave with his newborn twins. But his decision to do so showed something distinct about American family policy: It may be flimsy compared with that of many other nations, but it has tended to recognize caregiving as something everyone does, not just mothers.

The Democrats’ safety net spending plan would expand and cement this idea. Its family policy proposals — for paid family leave, elder care, child care, public preschool and a child allowance — together define caregiving as a universal need, regardless of gender.

Paid family leave would be for a wide range of circumstances, including births, illnesses and caregiving for extended family, in-laws, domestic partners and people who are the “equivalent” of family. The plans for child and elder care do away with the assumption that there is a default family caregiver — a mother or daughter. Instead, they direct support to the person needing care, by subsidizing child care or home health aides. The expanded child tax credit works the same way. The money goes to a child’s primary caregiver, including grandparents or fathers, instead of being targeted at mothers, as federal cash assistance for children has been in the past.

“A lot of the Biden agenda is really constructed around kids, and because it is, you lose some of the distinction around mothers and fathers, and you lose some of the distinction between single-parent and two-parent families,” said LaDonna Pavetti, vice president for family income support policy at the Center on Budget and Policy Priorities.

States have also taken a gender-neutral approach to family policy, and it sets apart the United States from other rich countries. Even though the U.S. is an outlier in its lack of support for working families overall — most Americans have no paid leave or significant financial help with child or elder care — American policies have been much more likely to include men from the start. (Washington, D.C., where Mr. Buttigieg lives and works as transportation secretary, provides eight weeks of paid parental leave to both fathers and mothers and those who have adopted or are foster parents.)

In much of Europe and the rest of the developed world, these policies are more likely to have been initially designed for women. As a result, they have sometimes reinforced gender inequality, by causing women to earn less and to be excluded from positions of power, and making it harder for men to be involved in their families’ lives.

Other rich countries have much more generous policies for men: On average, fathers have two months of paid leave. In South Korea and Japan, they have a year, and in France, seven months. Yet to get there, countries have amended policies to encourage men to use them — like “daddy days” of paid leave in Sweden, Norway and Canada that the family loses if fathers don’t take it.

Paradoxically, the reason the United States has been early in taking a gender-neutral approach to family policies is that it has been so late to offering them at all.

“This gender-specific approach lasted much longer there than here in the U.S., where the second wave of feminism took root sooner and successfully advocated for gender-neutral polices,” said Ruth Milkman, a distinguished professor of the sociology of labor movements at CUNY. “This is the one area in which the U.S. was ahead of the curve.”

A core idea of President Biden’s family policy plans is that caregiving is something everyone does. Democrats have framed the need as an economic one, as opposed to a women’s issue.

Politically, this approach is likely to be more difficult than focusing on mothers alone, researchers said, in part because it challenges preconceptions about gender roles. But they also said that by including more people, it acknowledges the needs of modern-day families, and perhaps makes it less likely that mothers are penalized for caregiving.

“Including these broader categories has made it a much heavier lift, but it’s been important to do that,” said Jane Waldfogel, a professor at the Columbia School of Social Work studying family policy. “There’s a cost of gender neutrality, but there will be a payoff for it in the end.”

The lawmakers driving the legislation reflect the idea that caregiving isn’t exclusive to women. Many leaders of this effort are women and mothers. They include Representative Pramila Jayapal, Representative Rosa DeLauro and Senator Patty Murray, who once taught preschool. But the effort has been led by Mr. Biden, who speaks openly and often about his experience as a single father. And men have been central to drafting the legislation for paid leave (Representative Richard E. Neal); child care (Representative Bobby Scott); and elder care (Senator Bob Casey).

There has been a longtime tension in family policymaking between whether policies should treat men and women the same, or recognize the differences between them in terms of pregnancy, childbirth and caregiving responsibilities.

“There’s been a shift back and forth in terms of the emphasis being on equal treatment, or that sometimes you need to recognize difference to get to equality,” said Dorothy Sue Cobble, a historian of feminism and labor studies at Rutgers.

The first major family policies, in the early 20th century, were aimed at protecting mothers — certain ones, at least. States offered mothers’ pensions, mostly for white women whose husbands had succumbed to one of the four Ds — death, disability, drunkenness or divorce. Black and Hispanic women were excluded. The first federal welfare benefits in the United States came in 1935, and included Aid to Dependent Children, “to enable the mother to stay at home and devote herself to housekeeping and the care of her children,” according to Social Security documents from the time.

Mostly, though, American policy has followed the approach of treating male and female caregivers the same — if only by not offering much support for either.

“In Europe, being a feminist meant talking about women’s caregiving responsibilities, and in the United States, we didn’t want to talk about those,” Professor Waldfogel said. “We went way farther than other countries in terms of equal rights, but less far with things like paid leave.”

During the world wars, many European countries had family policies like paid maternity leave and public child care to support the women who were doing men’s former jobs while they were deployed. These countries made them permanent in part to try to increase fertility after the losses sustained in the wars.

American women were involved in the international Maternity Protection Convention in 1919, which called for 12 weeks of paid leave for birth mothers, but while other countries followed it, the United States did not. And though the U.S. offered public child care during World War II, it ended after the war.

By the time the United States began offering unpaid leave for some workers, in 1993, and California became the first state to enact a law to pay for it, in 2002, gender roles had changed in major ways. Most mothers were already working for pay, and men were more involved with family. So the policies included both men and women, as well as caregiving for family illnesses, from the start.

Making policies gender neutral, though, doesn’t necessarily mean both men and women will use them. The backlash to Mr. Buttigieg’s leave shows how deep the resistance can be: “Paternity leave, they call it, trying to figure out how to breastfeed,” Tucker Carlson said on his Fox News show.

Today’s safety net programs are technically open to any parents, and yet it’s mostly mothers who sign up. Though state paid leave programs increase leave-taking by both men and women, women take longer leaves.

“There’s nothing that excludes fathers, but we know that often programs that have primarily served women don’t feel welcoming to men,” Ms. Pavetti said.

Policy design makes a difference. Women are more likely to work for pay if they can find high-quality child care that costs less than they earn. Men are more likely to take family leave if it’s paid and has job protection (the plan Congress is considering has the former but not the job protection.)

“Now we’re in this moment of trying to rethink what the social safety net looks like,” said Elisabeth Jacobs, a senior fellow studying family economic policy at the Urban Institute, “and how that matches where families are today.”