Ricky and Royce Marnell, 28-year-old fraternal twins from Orlando, Florida, have seldom done anything apart. Together, they competed on the wrestling team throughout their childhood and adolescence. On weekends, they’d venture to the nearby park to play football. When boredom struck, they’d head to the garage for a friendly game of ping pong. When it came to college, the brothers attended Florida State University (which they swear was merely a coincidence), where they also roomed together. Although they have different careers as adults — Ricky is a data analyst and Royce is a 3D artist — they find time to collaborate on a podcast about their twinness. They also share the majority of their friends.

Although the twins were in separate classes in elementary and middle school, Ricky took the lead on cultivating friendships. Royce was shy and uncomfortable, and he struggled to form social connections. So when Ricky, the extrovert, made plans, Royce tagged along. “It was also just always easier to lean on Ricky and just be friends with his friends because I didn’t have to put in any work,” Royce tells Vox. “They were always there.”

In college, they moved as a unit, picking up friends wherever they went — at orientation, outside of the dorm, in the elevator. At Ricky’s recent bachelor party, almost all of the attendees were mutual friends made during undergrad.

From birth, twins’ lives are inextricably linked. Brought up in the same environment at the same time, these siblings often inhabit similar educational, extracurricular, and social spaces, contributing to the expectation that twins share virtually everything, from interests to abilities. Because of this overlap, it makes sense twins would have overlap in their social circles, too. But as twins age and forge unique identities in young adulthood, they may find themselves making friends independently for the first time — a shift impacting both the sibling and friend relationships.

Being a twin doesn’t necessarily help or hinder the friend-making process, experts say. But having a constant companion may influence how twins approach friendship. When twins actively want to be more alike, they develop a common social network, according to research. At the same time, they often acknowledge being too dependent on one another, which might hold them back from making more friends.

“The research has shown that there’s no difference in the numbers of friends, but the closeness piece may be a little bit different,” says Laurie Kramer, a professor of applied psychology at Northeastern University. “If you have someone who knows you so well…that you really trust and feel like you can confide in, you’re probably not going to need that many other friends in your life to have that kind of deep friendship, intimate friendship with.”

When it comes to twin social circles, there is plenty of overlap, but twin type impacts the extent of the commonality. Studies have found that identical twins share a majority of their friends while cross-gender fraternal twins had far less overlap.

“If you think about identical twins, they are genetically the same. Their similar genes predispose them to like similar places, people, and events. So they naturally gravitate towards the same kinds of people,” Nancy Segal, a psychology professor and director of the Twin Studies Center at California State University Fullerton, tells Vox. “Fraternal twins tend to go in different directions. They tend to have separate friends, and this is a trend that seems to remain fairly stable across the life span.”

Having a shared social network is usually a matter of convenience. One twin is usually more outgoing, Segal says, and may take the lead when making friends, especially if they’re in the same class as children. Even if they move in different social contexts and form relationships independently, it’s hard to avoid the other twin during playdates at home.

Ironically, when kids are younger, they’re more likely to set clear boundaries with their twin, Kramer says: I want to play with Carly by myself today. Or they may hang out at their friend’s house without telling their sibling. It can be helpful to have these same frank conversations as they get older if they want to forge an independent relationship with a mutual friend.

In middle school, Royce Marnell remembers Ricky attempting to set such a boundary with him. Every day before class, Ricky and his friends would wander the halls with Royce tagging along. Ordinarily, it wasn’t a problem, but every once in a while, Ricky would tell his brother to kick rocks. “Ricky would just whisper in my ear, like, ‘Let me have this morning to myself,’ or ‘I want to talk to them about something and I don’t want you to be there,’” Royce says.

“Dang, I don’t remember doing that,” Ricky says. “I don’t really remember isolating Royce from my friend group because there was always guilt associated with that.”

That guilt was often reinforced by others in their lives: their parents and mutual friends asking why the other wasn’t invited. If Ricky wasn’t available to hang with a friend he made independently, the kid might reach out to Royce as backup. Their social lives, at times, felt out of their control.

When a classmate only wants to befriend one twin, the rejection can send the other into a tailspin — because despite their perceived similarities, someone clearly prefers one to the other. “The existential questions about who we are and our personalities and [which] people like us, it heightens those concerns in a way that I think people with a different-age sibling just don’t [understand],” Kramer says. (As with all relationships, it can be difficult to articulate those unintelligible, intangible qualities that attract you to someone and repel you from others, even if they are a twin.)

By high school, twins start to forge their own paths and consider who they are as a unique individual opposed to a unit. Through a process known as deidentification, twins might play up their differences to minimize competition and jealousy, by, say, enrolling in different classes and extracurricular activities. “We see that during that time, there may be much more of an interest in each twin developing their own friendships,” Kramer says.

In college, this separation intensifies if the siblings attend different schools. On their own for the first time — not as one half of a pair, but as just another student — they embark on a potentially new experience of making friends solo. In her research, Kramer says fraternal twins are more eager to break free from their sibling, as opposed to identical twins who understand the inevitability of independence, but want to delay it.

This interdependence might hold twins back from expanding their social networks. In Kramer’s research, identical twins who attended the same college reported relying on their twin in moments of loneliness, perhaps to their detriment. “Some of them did say that they felt a little bit too comfortable with this arrangement because their sibling was always there and available,” Kramer says. “It didn’t put as much of a pressure on them to go out to be a little more extroverted than they might ordinarily prefer.”

Because the reality is, twins will have to live independently, even if they continue to live near (or with) their sibling. Employers and significant others typically don’t look for pairs. Having the social skills and confidence to forge new relationships without their twin as backup is valuable in the long term.

It took until college for Jaclyn and Nick Lore-Edwards, 26, to transition from being known as “the twins” to simply “Jaclyn” and “Nick.” Growing up, the siblings had mutual friends; Jaclyn initially formed the relationships in elementary school, and those kids eagerly welcomed Nick. They both had the same interests — theater, books, dance, piano — and genuinely enjoyed being around each other, so they never had a reason to hang out with separate people. Being a twin meant strength in numbers.

“If I’m joining a new club and I don’t know if I’m going to know anyone, at least my brother is there and I can talk to him so I’m not just sitting by myself,” Jaclyn, a video editor and comedian, says. “I feel like that was definitely a big anxiety relief for me to always have him there.”

In addition to going to different colleges, their interests eventually diverged, and Jaclyn and Nick started meeting new people. Nick got involved with campus politics and model UN, while Jaclyn leaned into film and art, and each formed friendships with similarly minded people. Still, the act of making friends on their own was a relatively new experience. Having a twin, they say, was good practice for how to be a friend, not necessarily how to make them. “That was probably the first time I felt I have to do this alone,” Nick, a data scientist, says. “I can’t just rely on my sister to start talking to someone.”

While Jaclyn was the initiator in childhood, Nick thrived on his own in college: He came out as gay and gained confidence in himself. The friends he made knew exactly who he was and loved him for it. Jaclyn sensed that their high school friends, and by some extension her, had lost their luster, that the conversation really wasn’t that deep. “I could feel, when he would come home, maybe a little less interested in being with our friend group,” Jaclyn says. “That hurt my feelings. Me and you are best friends. But it wasn’t about me and our friends. He finally felt, I think, good at college.” Meanwhile, Jaclyn’s social circle was more intimate than Nick’s wide-ranging cohort, she says; her preferred friendship style mirrors that of a twin relationship. “I like having one really close friend or one person to go do stuff with,” she says.

Although they both live in New York City, they’ve still maintained their independent college friend groups. They represent the unique, individual adults they are now, not the packaged duo they once were.

While college was a period of mutual friend-making for Ricky and Royce Marnell, the twins from Orlando, their social lives did eventually split once they entered long-term relationships; their partners brokered their new adult friendships. After spending the first two decades of their lives under one roof, the Marnells now live with their significant others and with that comes responsibilities and obligations beyond their twin. Ricky’s planning a wedding; Royce just moved.

As a result of their progressing romantic lives, their shared experienced one has seemed to fracture. They don’t spend as much time with their mutual friends — if they do, it’s when college pals come to town — and instead most of their socializing is done with their respective partners’ friends. Before Ricky’s recent bachelor party, their group hadn’t gotten together in a handful of years.

“I wouldn’t say it’s harder to make friends now without Ricky,” Royce says, “but I would say it feels more lonely.”

This story was originally published in The Highlight, Vox’s member-exclusive magazine. To get access to member-exclusive stories every month, become a Vox Member today.