One warm night last August, James Hyde learned that his sister Justine was disappearing.

In a way, he had expected it. Eleven years her senior, James had always felt protective of the little girl who hated wearing dresses and wouldn’t comb her hair, who was awkward and ungainly, who prized the life-size Xena: Warrior Princess cardboard cutout she kept in her room, and who bore the brunt of their parents’ scorn and displeasure. When, at age 19, Justine came out to James as a lesbian, his response was, “No shit. I already knew, and I couldn’t care less who you find attractive.”

So, on that late-summer night, over black coffee in a Caffe Bene near Herald Square, when Justine said in her offhand, breezy manner, “Yeah, so, I think I’m going to go down to Callen-Lorde and get on male hormones,” James’s response was equally breezy and accepting. “You just told me that you’re transitioning to be a guy?” he asked, naming the moment. “Well, that’s awesome. Good for you.”

But James understood, in an intimate way, that the moment was crucial. He knew the fear Justine needed to overcome to say those words. He even knew Callen-Lorde, the clinic where Justine would soon begin receiving testosterone injections. For the past three months, he had been going there every two weeks for one milliliter of estradiol valerate. At the moment Justine told James she was transitioning, James was secretly already in the process of doing the same.

By the time they left the café, James had agreed that from here on out, he would call Justine “Felix.” That night was the last time he thought of his sibling as “her,” the last time he used her birth name, the last time Justine existed outside his memory. His sister wasn’t really disappearing, James realized. She was already gone. And though Felix didn’t know it yet, James was too.

Back in March, when Matrix director Lilly Wachowski came out as the second Wachowski sibling to transition, the media may have been shocked, but the trans community wasn’t. Go to any conference of transgender individuals, and you’ll probably see pairs — fathers and sons, mothers and daughters, spouses, siblings. Though no conclusive data exists, studies estimate that between 0.2 and 0.3 percent of the American population is transgender. That would mean the chances of both kids in a two-child family being transgender would be about 1 in 180,000. With those odds, hundreds of such siblings may exist in America.

One popular theory of transness, that it’s caused by a rush of hormones in utero — a mother producing too much testosterone or estrogen — would make sense for the Wachowskis, who both transitioned from male to female; but it doesn’t seem to work for a situation like the Hydes’, where the genders are opposite. Even children who had the exact same fetal conditions and genetic makeup don’t reliably have the same gender identity: If one identical twin is trans, the other has only a 20 percent chance of being trans too. (Felix and his sister, who chose the name Jeena, have three other siblings, none of whom they believe to be transgender.)

“Felix was so obviously not a little girl,” Jeena says. “But when you look at pictures of me as a boy, you wouldn’t say, ‘That’s a girl.’”

Nevertheless, the scientific community is coming around to the idea that transgender identity is biological. “Up until quite recently, and still in many conventional medical circles, the thinking has been that gender identity is some malleable process that can be manipulated externally,” says Dr. Joshua Safer, an endocrinologist at Boston Medical Center who specializes in gender nonconformance. “The medical establishment was very convinced that either gender identity is a construct that we’ve simply designed as a society — that it is nurtured in the environment — or that it is some passive thing where people look at their body parts and go with what they perceive the situation to be.”

But just because gender identity has a biological basis doesn’t mean that we know how exactly it works. “There are things that seem to correlate a little bit this way or that, but there isn’t a very clear picture,” Safer says. Some studies have shown that the white matter in the brains of trans males looks a lot like the white matter of biological men; but brain matter is malleable, so brain variance could be an effect, not a cause. Other studies looking at genetic females who were exposed to high doses of testosterone in the womb found that only a small minority turned out to be trans — but that small minority was still substantially higher than the percentage of trans people in the general population, implying that the hormones did have an effect, but possibly only on individuals who already had a genetic predisposition. And even if these causes do account for some causes, it’s a small minority of all trans people. “Most transgender individuals haven’t had anything abnormal that we can see,” says Safer, who believes there is probably no single cause that can be isolated. “I don’t know that it’s likely that we’ll ever get so lucky as to simply be able to identity a gene or a region of the brain” that determines gender identity, he says. “That’s still a fantasy. In terms of explaining the actual mechanisms for gender identity, the medical community is at a pretty rudimentary stage.”

None of this matters to Jeena and Felix. Though they recognize the rarity of their situation, they don’t feel the need to explain it. “It’s kind of like magic,” Felix says. “Filipino magic.” They’re quick to point out the ways in which their paths to transitioning have been different. Part of it is generational: Jeena, now 41, is a Gen Xer, who learned she was trans by going to the library and reading about sexuality; Felix, 30, is a millennial who came of age in an Internet world. Before her transition, Jeena largely dated women, to the extent that she dated at all, while Felix has mostly identified as gender queer and polyamorous (he prefers butch women and trans men to femme women and genetic men). Though they don’t know whether it’s a function of generation or personality, Felix always seemed unable to mask his true identity, while Jeena — the favorite of her parents, the child who got good grades and won spelling bees — was expert at it. “Felix was so obviously not a little girl,” Jeena says. “But when you look at pictures of me as a boy, you wouldn’t say, ‘That’s a girl.’”

Their parents met while their dad — a midwestern “hick from the sticks,” as Jeena puts it — was in the Navy, stationed in Manila during the Vietnam War. Back home, he was in and out of jail, often for writing bad checks, while Jeena and Felix’s conservative Catholic Filipino mom was left to keep things together, working two jobs as a janitor and suffering from what both children believe to be some pretty hefty undiagnosed mental issues. Sometimes there wasn’t enough money to keep the lights on.

Photograph by Ryan Pfluger

Around the time the family moved from Indiana to settle in “the dirt and weeds of Bumfuck, Florida,” Jeena stepped in to keep Felix from becoming entirely feral. She taught him to read before he started kindergarten. She crawled into his crib to sing him to sleep. From Jeena, Felix developed a taste for video games and anime and Guns N’ Roses’ Appetite for Destruction, which he called “the ghost tape.” And when their parents were cruel and punishing to Felix — when they berated him for being chubby or clumsy or otherwise less than ideal — she tried to make up for it, to let him know that he’d be okay in the end.

Jeena, meanwhile, hid her adoration of femininity behind friendships with church girls, who prayed for her to accept Jesus as her savior over midnight breakfast at Denny’s. By the time she began visiting strip clubs just to talk to the dancers about her secret (“Like a lot of trans people, I sought at first really cliché depictions of femininity”), she was in college — old enough to hide her secret from her family. “Felix got shit on because he was obviously not a heteronormative, cis-normative type of person,” says Jeena. “I told him that our parents were the ones who were wrong and being assholes. But I always felt bad not telling them, ‘Hey, fuck off, guess what? Your fucking favorite kid was born in the wrong body and is going out at 21 years old, cross-dressing, having sex with men, because he’s actually a she. It was such a double standard that our private behaviors were similar, but we were being treated by our families completely differently.”

When Felix’s parents tried to send him to a camp to pray the gay away at age 18, he left home for good. At 20, he tried to commit suicide. “Everything was super-depressing,” he says. ‘Like: ‘I don’t know how to be in this world. How do I even live this life? This blows.’”

Jeena remembers that phone call — when she learned about the suicide attempt and that Felix had been involuntarily committed to a psychiatric hospital — as one of the worst moments of her life. They had fought over money Felix owed Jeena a few days before. “Of course he didn’t do that because I gave him shit,” Jeena tells me. “But my heart fell right through me.”

As siblings sometimes do, they drifted in and out of each other’s adult lives, losing touch for several years when Jeena was in her 30s and didn’t know how to extract herself from a relationship that had turned emotionally and physically abusive. When she finally broke it off and decided to start fresh in New York, the fact that Felix was there was a “huge factor” in her choice.

Felix was more skeptical. “I don’t really feel any particular affection for or obligation to someone just because we share a lot of genes,” he says. “Until Jeena moved here, I hadn’t really seen her since I was 22, and we’re very different people.” The two spent several months getting reacquainted as James and Justine, exploring the city, trying new food, and rediscovering a familial rhythm, eventually moving in together. Jeena says they got along well, only fighting over “usual roommate stuff,” like who paid what bill, Jeena’s cleanliness, and Felix’s lack thereof. For Jeena especially it was a relief to have some part of her family back.

But still it took her a while to come around to the idea of coming out. Even though Jeena knew that Felix, of all people, would be accepting, she didn’t initially feel psychologically prepared to share her secret with anyone in her family. She was still presenting as a man. She still had a beard and a little bit of male-pattern weight she wanted to lose. And she was still holding on to the idea that she would morph from James Hyde into Jeena Bloom — the last name a nod to both Joyce’s Ulysses and Bloomington, the small town in Indiana where their family had lived — alone, in secret, in a little bubble she could emerge from “fully formed.” Felix’s transness forced the issue: If Felix was finding his real self, Jeena felt her own male socialization might come in handy. More to the point, if they both were going to transition, she realized, they may as well do it together.

Three weeks after that conversation in Caffe Bene and about a week before the siblings signed a lease on a two-bedroom garden apartment in Crown Heights, Jeena sat Felix down in another coffee shop in another part of town, showed him a picture of herself in femme, and told him that she not only was transitioning but had been for months.

“I was super-surprised,” Felix says. “Like, Whoa, really? Fucking awesome! I don’t know what our parents did, but they obviously did something super-right.”

As they came to discover, their parents were also the reason both siblings had postponed their public transitions: Neither felt like they could come out as trans while their parents were still alive (their dad died of heart disease in 2005; their mom of cancer in 2012). Both had waited until they moved to New York, until they had steady jobs with health insurance that would help cover the cost of hormone-replacement therapy, and until they had extracted themselves from unhealthy relationships with people who hadn’t wanted them to transition or who denied that they were trans at all. This month, Jeena’s stock options at the internet company where she works as a technical engineer vested, meaning that when she comes out at work, she’ll have $10,000 at the ready should things go south. She doesn’t anticipate that anything truly unpleasant will happen, but it’s good to have a cushion, just in case.

The fact that Felix was already viewed as butch — combined with the fact that, culturally speaking, a woman in pants and a flannel doesn’t raise many eyebrows — has made his gender transformation seem far less abrupt and disruptive than Jeena’s. His main reservations about getting on testosterone were philosophical rather than practical. Before dropping out of college, he’d been a women’s-studies major. “Part of the reason I waited to start hormones was that I had a really weird relationship with my masculinity — like, men are terrible, and I’m a man. I didn’t know how to reconcile my feelings.”

Sometimes he still doesn’t. “I just don’t want to be that kind of guy who’s, like, a gross dude.” But once the decision was made, he didn’t have the same hang-ups as Jeena did about coming out to any- and everyone. The very day he got his first injection of testosterone, he changed his Facebook status to “male.” Then he mostly went on about his business.

For Jeena, it doesn’t feel so easy. “I’m not trying to take credit for his life, but he became confident in who he was because I tried not to judge him and to make him feel okay,” she says. Jeena didn’t have a similar familial figure to look up to. She’s spent more years of her life inhabiting a body she doesn’t see as her own. Both physically and emotionally, she feels like she has further to go.

On the third floor of a West Village walk-up, Jeena is getting ready to meet Felix for the first time in femme. Though she came out to him more than five months ago, she hadn’t wanted him to see her as her until she had mastered her image. “I just wanted to have everything really solid,” she says. “I wanted to be very confident so that when we were out together, and I was meeting his friends and he was meeting my friends, that it doesn’t seem weird or halfway done.” A few months ago, after reading a profile in this magazine, she’d reached out to feminine-image consultant Monica Prata and begun the process of polishing her look, her way of presenting herself.

Photographs by Ryan Pfluger

Now she perches on a seat in front of a mirrored vanity, inspecting her face. Laser treatment two days ago has left her jawline a little red, but Jeena knows she has the luxury of shifting into a stereotypical feminine form. She’s five-foot-nine and wears a 9½ in women’s shoes. Her face is delicate even without facial feminization surgery. She’d like to have her breasts done but wants to wait to see what hormones do first. She’s become comfortable enough in her skin that she recently started dating in femme, though her OkCupid profile is quick to point out that she’s in the process of transitioning, not fully out, and might be “kind of a mess right now, but then again, who isn’t?”

Both Jeena and Felix came out to friends socially before coming out to each other. “It is a big, symbolic moment,” Jeena says. “Felix is the first person in my life that I didn’t meet this year that is going to be a part of this part of my life now, and he’s going to be the first of my immediate family to see it. This is my old life and my new life coming together.”

Which requires the right look. After Prata helps her into breast forms and the requisite padding, Jeena slips on a form-fitting Rebecca Taylor dress and an edgy pair of open-toed heels (“I did go to the trouble of having my toes done”). She smooths down her wig, which she had cut the day before into an approximation of what her own hair will look like once it’s grown out. Then she studies her reflection in the mirror. “What do you think?” she asks tentatively.

Prata cocks her head to the side in approval. “It’s kind of a shame we’re going to meet your brother now,” she grins. “You look a little too hot.” Jeena meets her gaze and smiles back.

An Uber ride later, Jeena is making her way carefully through the crowded bar of a West Village hot spot when she sees Felix at a table in the back.

“Who-oah!” he says, standing to greet her. He looks her up and down and then, with acceptance but no fanfare, provides the simplest of verdicts: “That’s a sweet coat.”

Then, as if they’d known each other as Felix and Jeena their whole lives, brother and sister sit down to eat.

Three nights later, Felix and his handsome, nonmonogamous girlfriend Danielle — a gender-queer 24-year-old from Pennsylvania who loves her boyfriend’s newly sprouted “sweet little mustache” — are cooking up a vegetarian feast in the small kitchen in the back of the Crown Heights apartment, while Jeena drinks wine out of a Solo cup in the living room next to their rescue dog, Lorenzo. Besides Felix’s room, which looks like a bomb went off in a Foot Locker (“The only way he’s girlie is in the amount of shoes that he owns,” Jeena teases), the apartment is immaculate. It’s also in its own state of transition, with Jeena phasing out the bachelor-pad look in favor of flowery bedspreads and ornate furniture and art. While the siblings realize that their little garden apartment in Brooklyn could be considered a gender experiment of the highest form, it doesn’t feel that way to them. “When we hang out, we don’t talk a whole lot about our transitions,” says Felix. “We still talk mostly about, ‘Oh, I saw this TV show,’ or like, ‘This person sucks.’”

“I felt separated from him by age and culture — he was out as queer and I was not. Now we are in this together.”

Tonight isn’t entirely standard, though: This is the first time Jeena has spent an evening at home with her brother in femme, so they’re conducting what they call a “State of the Union chat” about their transitions. “I definitely think hormone-replacement therapy has made me more chill in a way that I didn’t expect,” says Felix, after delivering plates filled with tempeh, kale, and plantain chips. “I’d always been under the assumption that my biology did not determine my personality, because of, like, free will. Apparently I was wrong. I don’t remember the last time I cried, and I used to cry a lot.”

“I think that’s the confirmation of your transness,” assures Jeena. “Your brain is like, ‘Oh, finally, I’m getting chemically what I’ve been desiring forever.’ I do feel more collaborative and more open and more communal than I used to.”

“I’m glad that I have lived in the world as a female person,” Felix says, as his sister nods in agreement. “It makes me less of a piece of shit. I just think that if I had always been male, I would not perhaps respect women the way that I do, and I would maybe not be a feminist.”

Jeena rolls her eyes sympathetically. Since she started dating in femme, she’s gotten dick pics from strangers and had many men tell her to smile. “And there are differences in the way I’m treated,” she says. “Like, I went on a date with a guy last year and I told him what my job was, and he was like, ‘That’s cool,’ and then he starts explaining to me how the internet works.”

“Did you tell him to die? I hope you told him to die.”

“No, I fucked him, because I was horny,” Jeena says as Felix cracks up.

“I have the opposite happen at work,” Felix offers. “Everyone thinks I’m the smartest dude now. I didn’t do anything. I just read you back what a woman said to you. I read it in my man voice, and now you can understand it.” He shakes his head. “Being a woman sucks.”

Jeena can’t argue with that, but she’s happy to have Felix validate her experiences — and in turn to validate his. To the extent that their relationship has changed, it’s become more equal. “I’m less the older sibling than someone in the same fight as Felix,” Jeena says. “I felt separated from him by age and culture — he was out as queer and I was not. Now we are in this together.”

We’re at a karaoke dive the next night when — some time between Felix’s rendition of “Ignition” and Jeena’s “Beautiful” — it becomes clear just how lucky the pair got with this improbable roll of the gender identity dice. Jeena rocks a sleek blazer. Felix wears a sideways cap and a perpetual grin, his arms draped around Danielle. Across the tops of beer bottles, Jeena looks over at her brother gratefully. Their old selves might have disappeared, or be in the process of disappearing, but something more authentic is happening now. And for each of them, someone is there to take notice, to create continuity, to keep them from being alone. “It does make it easier to come home and be like, ‘Oh, you know what I’m going through — but, like, opposite,” says Felix. “Yeah, it takes the pressure off,” agrees Jeena.

Her song comes up: “Closer to Fine” by the Indigo Girls. She rises from the banquette, grips the microphone in her hand, and turns to face her brother. “All right, Felix,” she grins. “This one’s for you.”