Love in Your Family Line: Birth Order and Romantic Tendencies

From class year and major to political affiliation and spoken languages, we ask a lot of good ol’ get-to-know-yous on the Marriage Pact questionnaire. Luckily, one of the first questions students are faced with answering is also one of the easiest: I am a(n) ______ child.

There are any number of ways an only child might find themselves to be different from the youngest child of three or the oldest of seven. We’ve already explored the validity of birth order stereotypes using Marriage Pact survey data. However, we thought we’d return to this question to see whether or not a person’s birth order specifically impacts their romantic tendencies and behaviors in a relationship.

To determine this, we looked at the average Marriage Pact survey responses of students of different birth across a few different categories: security in relationships, authenticity and affection, future goals and desires, and sociosexuality and monogamy.

At Villanova, only children consistently value authenticity and affection in relationships over students of other birth orders, providing the highest average responses (on a scale of one to seven) for the following questions:

  • I say what is bothering me, even if it makes my partner uncomfortable

  • I like to play games that involve disclosing intimate thoughts and feelings

  • A long-term relationship should be founded in… [one = practicality, seven = passion]

Only children at Villanova also consistently answered higher than students of other birth orders for questions about feelings of security in relationships, such as:

  • Flirting is a form of cheating

  • I can’t go to sleep if my partner is upset with me

  • Do you believe in soulmates? 

Across schools, there were fewer consistent category-wide trends. At Villanova, Brandeis, and Clemson, however:

  • Only children value having a 5-year plan and want the least amount of children

  • Youngest children would send a relative to a nursing home

  • Middle children would go to sleep with their partner still upset with them

  • Oldest children are the least interested in a long-distance relationship or non-monogamy and are the most likely to want to settle down in the city 

    birth order kids

At each school, the Marriage Pact questions that saw the greatest numerical range of responses between students of different birth orders were I would be disappointed if I didn’t meet my Marriage Pact, I would move somewhere where I don’t know anyone, and I like playing games that involve disclosing intimate thoughts and feelings. 

birth disapointed
birth movesomewhere
birth games

Katherine Luong, a researcher on Marriage Pact’s Relationship Science team, explained that while we don’t account for birth order when assigning compatibility scores, it does have its uses. 

It’s kind of a user-experience thing. People like answering questions about themselves. Another aspect of the questions is that this data helps us if we ever wanted to run our own research, but right now the question isn’t used for making matches.

While Marriage Pact survey data shows a few differences in romantic tendencies across different birth orders, other research hasn’t been conclusive.

It seems that birth order can affect your relationship with your siblings, parents, and your childhood friends, but that’s a very different context from romance. Generally, people’s personalities change drastically when they’re in different positions of power. For children, once you become a parent, you’re not necessarily going to fill the same role you did when you were a kid. There have not been any significant findings that say that birth order is the reason that people act a certain way, in romantic relationships, at least. 

So what does that mean for the stereotypes associated with family dynamics? Do they correlate with or influence certain behavior in relationships? The short answer is no— unless someone really, really believes that they do. 

It’s unlikely that the roles and behaviors from someone’s childhood as they relate to their siblings will affect their role in romantic relationships. But there is a philosophical thing about stereotypes: people tend to act in accordance with them.

Just the fact that [a stereotype] exists can create a kind of placebo effect, where there are differences that are perceived to be there even if they’re not, which causes those differences to exist anyway. So it is totally possible that if people really believe that their birth order matters, it does end up mattering. Conception is reality and all that. That’s not backed by data, but it could explain why people are able to bond over their birth order.

While the behaviors and personality traits associated with specific birth orders don’t necessarily correlate with behaviors in a given relationship, could birth order itself be indicative of compatibility?

For example, is a couple that consists of a youngest and oldest child more compatible because of complementary traits, or will a couple that consists of two oldest children be more compatible due to shared experiences?

I don’t think that birth order and family dynamics would affect romantic compatibility, at least in terms of long-term compatibility. I think it’s something that people can bond over in the short term, which does pave the way for long-term relationships, but it’s one of those similarities that hasn’t been shown by research to be as important as other things… but in relationship psychology, similarity is indicative of compatibility more so than dissimilarity. So if that were to apply to birth order as well, it’s unlikely that it would be opposite.

People’s personalities and values are informed by far too many things to be able to accurately assign a specific behavior to something like birth order. That question does remind Katherine of the concept of complementarity, though, which refers to how well people with differences in personalities, traits, or values fit together.

We did a lot of research into whether similarity is better or if complementarity is better. In general, similarity is better, unless you have two people with two very negative traits. If both people have those negative traits, the relationship will be bad. And one person having a positive trait and one person having a negative one will never be an ideal relationship, it will just be a little better than having two negative traits.

Essentially, the current scientific narrative behind birth order and its impact on romantic tendencies is inconclusive at best. That may be why there were few category-wide trends in how students of different birth orders answered Marriage Pact questions, and why none of those overarching trends existed completely across all three schools.

Katherine did, however, share a study that discusses how being raised with siblings may influence a person’s values.

A 2020 study found that only children give more importance to power values and give less importance to benevolence values than individuals with siblings. Power values, in our model, are things like ambition and interpersonal dominance. Only children are more likely to value those, and they’re less likely to value things like altruism and nurturance, and general benevolence, and caring about people outside of their family. 

These differences diminish gradually with age, which would explain why being an only child doesn’t impact long-term relationships, and why differences may be more apparent in younger people.

This idea echoes many of our findings from our first story on birth order stereotypes. In this batch of analysis, we found even more trends across all three schools. At Villanova, Brandeis, and Clemson, only children are more likely to say they have a 5-year plan, for example, which speaks to their ambition and desire for self-enhancement. They also want the least amount of children, which could be for any number of reasons, one of which may their general lack of interest in nurturance.

Your birth order may not be able to predict with all certainty what you’re looking for in a relationship, or how you’ll tend to behave once you’re in one. But it’s still interesting to take a look at what students across the country value and what they want from their relationships, no matter where they fall amongst their siblings.  

Have a question you’d like us to explore next? DM us on Instagram or Twitter, @MarriagePact.