There’s nothing Hollywood TV producers love more than a good rebellious-child story. In the 1970s, All in the Family’s Gloria embodied the Baby Boomers’ liberal rejection of Archie Bunker’s grouchy white working-class values; a decade later, Alex P. Keaton personified the young Reagan revolutionary railing against his aging hippie parents in Family Ties. Alex would often mock his parents’ earnest embrace of ’60s-style do-goodism. Regaled, yet again, with stories of protesting the Vietnam War, he quipped: “What were you protesting? Good grooming?”

But in the real world, Alex P. Keatons are surprisingly rare. When it comes to politics, at least, it turns out most of us are not quite as rebellious as we might like to think. The more prosaic reality is that husbands and wives, parents and children, brothers and sisters generally agree on the big issues of the day. But why? New scientific research raises tantalizing questions about the origins of our political leanings, including the intriguing idea that our politics could be baked into our genes.

The original insights into the relationships between family members’ political views date back to Archie Bunker’s day, and the pioneering work of political scientists Kent Jennings and Richard Niemi. Their innovative surveys started in the 1960s, when they interviewed both parents and children about their political beliefs, and then followed those children over time as they reached middle age. While they did indeed find that Republican parents tended to have Republican children and Democratic parents tended to have Democratic children—66 percent of Democratic parents had Democratic children, and 51 percent of Republican parents had Republican children—they also discovered some fascinating variation within that general pattern. For example, people with parents of different political parties were more likely to be moderate. And children whose parents were not particularly interested in politics themselves did not vote when afforded the opportunity.

But these interesting patterns left unanswered questions about the underlying reasons family members influence each other. Social scientists have recently begun to fill in those gaps. For example, John Hibbing and his co-authors argue in their recent book Predisposed that parents pass on their political beliefs to their children genetically. Their surprising results rely on studies comparing identical and fraternal twins to show that identical twins (who share more genetic material than fraternal twins) are also more likely to hold similar political views.

How can there be a party in your genes? Hibbings and his colleagues find, for example, that conservatives smell androsterone, a steroid hormone one-seventh the potency of testosterone, more readily, and conclude, rightly or wrongly, that this leads them to be “more comfortable with clear social hierarchies”—in other words, more authoritarian. As they put it: “We know that the world smells differently to some people than to others, and variations in the ability to smell androstenone might be related to political beliefs.”

Besides genetics, another reason why people in the same household might have similar political views is that they share the same environment and are affected by similar events. A terrorist attack or a steel plant closing, for instance, can affect the views of everyone in the same family. Or, if family members share certain traits (like skin color), they may experience similar challenges and difficulties in the world, thereby causing their views to converge.

The trouble is how to sort out these competing explanations. So social scientists often look for “natural experiments,” situations where an important variable is assigned at random. As it happens, nature assigns one key characteristic randomly: a child’s gender. By comparing families of the same size who had boys with those that had girls, we can see what effect that child’s gender has on the political beliefs of other people in the household.

The gender of children can have powerful consequences for a family’s political attitudes, these studies have shown. For example, Emily Shafer and Neil Malhotra reported in the journal Social Forces that fathers who have a daughter (vs. having a son) are more likely to hold egalitarian views on gender roles and women’s place in society. (There was no effect for mothers, presumably because they were already sensitized to women’s issues.) The same holds true for political and business elites. For example, Ebonya Washington reported in American Economic Review that U.S. congressmen are more likely to vote liberally on reproductive rights issues when they have daughters as opposed to sons. Having daughters is also associated with male CEOs who pursue greater gender equality in their employees’ wages, according to research by Michael Dahl and colleagues. And Maya Sen and Adam Glynn found that Republican male judges are more likely to rule in favor of women’s rights if they had a daughter.

But baby girls do not always have liberalizing effects. In a forthcoming study we conducted, we showed that having sisters actually made young men more conservative when it comes to gender roles and their party identification. Why? One potential explanation is that boys with brothers are more likely to be assigned household chores, while those with sisters are shielded from what is generally considered “women’s work.” Learning these patterns in childhood creates models for behavior in adulthood—and indeed, we also found that men with sisters were less likely to split housework with their wives than men with brothers.

While far from definitive, these results suggest that having sisters caused the boys to have a more traditional upbringing, and that in turn could have led to greater political conservatism. Or, it could be that older brothers are paternalistic and want to shield their younger sisters from dangerous influences. This paternalism might then carry forward and, years later, influence their views of women’s role in society and men’s responsibility to protect them.

All of this brings us back to Alex P. Keaton, who grew up with two sisters and turned out an unlikely conservative in a family of liberals. Our results suggest that is plausible: Having sisters could have made Alex a little more likely to turn out Republican. Of course, much more than sisterhood would also come into play: genetics, parental influence and shared environment would all help shape a real-world Alex. The old conventional wisdom was that family ties would push Alex toward his parents’ flower-child values. But there’s something else to consider: Sisterhood is powerful, in ways we still don’t really understand.

Andrew Healy is associate professor of economics at Loyola Marymount University and has a younger sister. Neil Malhotra is associate professor of political economy at the Stanford Graduate School of Business and has a younger brother. Both are political independents.