Being an only child can have a surprising impact on your love life, according to therapists

smiling couple sharing piece of chocolate while on date
What is the birth order dating theory?Thomas Barwick - Getty Images

Despite our four-year age gap, my younger brother and I are besties. And while some of my fellow firstborn friends find it odd, my brother and I openly talk about our dating lives. We tap each other for advice and certainly are not afraid to roast each other’s dating profiles. But one factor that neither of us considered impacting our love lives is our birth order.

If you spend any time on TikTok, you might’ve already heard of the birth order dating theory, which posits that certain birth order pairings are more compatible than others. The hashtag #birthorderinrelationships has over 58.6 million posts, with many users confirming that their past relationships corroborate the theory. “I am the eldest daughter, and all of my relationships have been with youngest sons,” revealed one user.

As it turns out, this theory isn’t just a fun TikTok trend—it’s psychologically backed, too. Your birth order has a direct impact on your personality and relationships, including who you date. “Your siblings can absolutely impact your romantic life, because those are your first age-appropriate dynamics when you’re learning how to communicate with someone,” explains Karen Stewart, PsyD, a psychologist specialising in sex and couples therapy in California. Therefore, it makes sense that eldest children are often drawn to last borns: “If you’ve been comfortable with that dynamic for the past 20-plus years, it isn’t surprising that you gravitate towards that type of partner,” she adds.

So, what is the birth order dating theory, and is it really the ultimate compatibility test? Ahead, relationship experts and therapists break it down.

What is the birth order dating theory?

The hashtag #birthorder may have 690.5 million views on TikTok, but the birth order personality theory has actually been around for over a century. The idea that children may inherit certain behaviors and traits based on where they fall in their family tree has its origins in the early 1900s.

Through his research, Austrian psychologist Alfred Adler—who is also credited for developing the superiority complex and retail therapy theories—suggests that the rank of one’s birth order shapes not only your personality, but how you show up in all aspects of life. In other words, my fearless ability to take charge is due to my inner “eldest child syndrome,” in which my role as the older sibling moulded me into being a leader and problem solver.

According to Adler, birth order can also impact how we view and interact in non-familial relationships, including romantic ones. More specifically, your birth order can explain compatibility with a partner, as an eldest child’s alpha mentality may best compliment the personality of a youngest sibling, who tends to be more of a follower. Although every family dynamic (and person!) is different, “there are common threads in all these birth order situations,” Stewart notes.

What can my birth order tell me about my relationship needs?

As for whether you should use the birth order theory as your love compass, well... let’s let the stereotypes do the talking, first. Ahead, everything you can learn about yourself (and how you show up in relationships) from your birth order.

Eldest child

As the eldest, firstborns can feel a sense of hierarchy over their siblings. “They’re used to being the leader,” explains Stewart.

While Adler’s birth order theory describes firstborns as being high achievers, problem solvers, and caretakers, Stewart says these strong characteristics can also result in controlling tendencies. Additionally, eldest children tend to be people pleasers and worrywarts, she adds. (And suddenly, my anxiety all makes sense!)

In the realm of dating, eldest children exhibit many redeeming qualities. For starters, they’re action-orientated—so if planning date night isn’t your thing, they’ll likely be more than happy to take the reins. Eldest children are also devoted and reliable.

While there’s nothing wrong with having an alpha personality, per se, the “need to be in control all the time” can also hurt you in a relationship, warns Julie Menanno, LMFT, a marriage and family therapist, and the author of Secure Love: Create a Relationship That Lasts a Lifetime. An eldest child might not know “how to adapt or be flexible with their partner,” which can lead to issues including resentment from their S.O., she adds. You never want your partner to feel like they’re “invisible” in the relationship, so try to relinquish some of that control when you can, advises Menanno.

Middle child

Growing up, middle children often get lost in the shuffle. “They don’t entirely know what their identity is because when they’re with an older sibling they’re treated like the youngest, but with a younger sibling, the middle child wants to exert that power or dominance of an older sibling and it’s really confusing for them,” explains Stewart.

Because of this constant tug-of-war, middle children often take on the role of peacemaker. “As a peacemaker, they tend to back away from conflict because they want everything to be okay. However, being the family peacemaker is exhausting for them, so they may view relationships, including romantic relationships, as a lot of work,” says Menanno.

Sometimes, this can snowball into developing poor communication skills like “checking out in the face of conflict,” she adds. On the contrary, Menanno says middle children may be more verbally combative in relationships because “they’re used to having to fight for their voice to be heard.” It'll likely depend on what your relationship with your older and younger siblings looks like.

Youngest child

Known as the “baby” of the family, last borns are often perceived as spoiled, extroverted, and a little rowdy, according to the birth order theory. Whereas their eldest siblings were held under a magnifying glass, the youngest are typically, in theory, kept on a looser leash. To put it simply, they’re able to get away with a lot more.

That said, last borns are used to adhering to multiple authoritative figures in the house, which can sometimes translate to codependency in relationships. On the flip side, “if you’re used to being spoiled and getting all your needs met, then that can turn into sucking up all the air in a relationship,” says Menanno.

But, of course, every partnership needs balance. A last born’s fun spirit and zest for adventure can be appealing to a firstborn or even middle child who considers themselves a rule follower. Their spontaneity ignites feelings of excitement and togetherness, both of which are important building blocks of a relationship.

Only child

Similar to last borns, only children crave the spotlight because they’re often used to being the centre of adult attention. “They’re used to having their needs met at all times, so those folks can tend to be a little more needy,” explains Stewart.

Only children can also get a bad rap for being selfish in relationships. “Stereotypically, only children don’t learn how to share in those formative years. Thus, for example, not learning how to share toys can evolve into not knowing how to share time or space with a partner,” continues Stewart.

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Communication can also be a weak spot for some only children. “This is particularly true when it comes to fighting styles, as only children can be more catastrophic with their words and actions,” says Stewart. But despite this, only children might also be more mature and emotionally intelligent in some ways, because they grew up surrounded by adults.

Which birth order combinations are compatible?

So, who is your “perfect” match based on the birth order dating theory? On paper, all signs point to firstborns and last borns being the most compatible pairing, says Stewart. “The eldest is used to assuming the role of caretaker. This person aims to please and they want someone who they can look after,” she explains. “Then, you have the baby of the family, who is used to being led and coddled. That’s a dynamic they’re [both] probably comfortable and familiar with.”

And the same goes for firstborns and only children: “An only child looks for someone who can take care of them at all times, which is one of the primary personality traits of a stereotypical eldest child,” says Stewart. While only children may run away from conflict, firstborns run towards it.

Surprisingly, middle borns also get along best with siblings who were born first. “The eldest can be the leader and the support system that the middle child never received growing up,” explains Stewart. Meanwhile, middle children are perceptive yet quiet. They make great mediators, which helps when navigating tough conversations in which an eldest’s instinct is to take control.

Which combinations *aren't* compatible?

Theoretically, based on the birth order dating theory alone, same-birth orders are the least compatible combinations, say both Menanno and Stewart. This means two firstborns, two middle children, two last borns, and two only children might not be the best match.

“Two older siblings together will definitely butt heads in a relationship,” says Menanno. “Both people have been awarded throughout life for taking charge, figuring it out, making a plan, finding a solution, and being the one that’s always right. And so, it feels very vulnerable to an eldest child to have to give that up.”

And, while being a peacemaker certainly has its attributes, a pair of peacemakers (I’m looking at you, middle children) can put a relationship in a communication rut. “They’re going to have a difficult time navigating conversations, especially big ones that may involve conflict,” warns Stewart.

And finally, because last borns and only children are used to being the centre of attention and share such similar personalities, any combination of the two could end in strife. But if you’re in a same-birth order relationship, don’t worry: This isn't an end-all, be-all compatibility test, because every person is a little different. “There could be a super healthy situation in which nobody needs to fall into those rigid birth order roles to feel a sense of identity or belonging,” says Menanno.

So, can your birth order really tell you who’s a match?

If you’re fascinated by astrology and/or attachment theory, then you know there are a lot of different factors that play into who we become in relationships, and birth order is just one of those. So, if you’re a firstborn contemplating whether you should dump your fellow firstborn partner because this theory is all over your TikTok feed right now, well… first, take a breath. And, no. Someone's birth order shouldn't be a relationship deal breaker, say both experts.

“Does [this theory] mean you should set up your dating profiles to ‘I only date the youngest child?’ Absolutely not, because we were all raised in different ways,” explains Stewart. While birth order does shed some insight into the role you might feel comfortable filling in a relationship, it isn’t the golden rule of dating.

Am I going to stop dating lastborns? Definitely not. As much as I hate to admit it, I do inhibit the caretaking (and controlling, if I’m being honest) gene. But, did Adler’s theory prompt me to reevaluate how I show up in relationships? Absolutely.

Meet the experts: Karen Stewart, PsyD, is a psychologist specializing in sex and couples therapy in California. Julie Menanno, LMFT, is a marriage and family therapist and the author of Secure Love: Create a Relationship That Lasts a Lifetime.

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