When I was a little girl growing up in Bulgaria, my best friends were two identical twins named Ema and Maia. If this alone didn’t already dangerously discombobulate the very notion of a “best” friend, the situation was rife with various other complexities of negotiating identity — theirs, as well as mine. I oscillated between being best-er friends with one, then with the other. I was furious with my mother for never having learned to tell them apart and often calling one by the other’s name. I found myself in frequent spirited arguments with other kids, determined to make them concede Ema and Maia’s vast differences of temperament and spirit. (The reality was somewhere partway between my insistent differentiation and the other kids’ insistent conflation.)

All of this I did in part on the twins’ behalf, for I believed it to be the chief duty of the twin-friend, and in part for my own benefit: Duality in any form is hard enough for adults to make sense of, but the constant scanning for sameness and difference, the reflexive dance with comparison and contrast, was too overwhelming for my eight-year-old psyche to comfortably sit with — to resolve the tension, I was bent on seeing them as categorically different; to resolve the tension, those outside the best-friends bubble were bent on seeing them as categorically the same. I — we — couldn’t understand, or perhaps couldn’t accept, that they were both tremendously similar and tremendously different, often at the same time.

Quite unexpectedly, Ema and Maia’s mother won a green card in the American lottery. The day the family moved from Bulgaria to Baltimore was among the saddest of my childhood. It was followed by many mostly friendless years, for no single person — no monad of identity — seemed a sufficient substitute for my dyad of best friends.

Of course, the identity ambivalences with which the twin-friend grapples are merely a microcosmic refraction of what the siblings themselves deal with daily. And yet to be in the mere presence of twins, let alone to negotiate one’s sameness and difference of feelings for each of the dyad, is to inevitably confront one’s own most unsettling and unsettled questions of identity.

These complex questions and a dimensional lot more are what writer Caroline Paul explores in Almost Her: The Strange Dilemma of Being Nearly Famous — a short and piercing memoir of her life as a twin. Amplifying the inherent complexities of twindom is the fact that her sister happens to be the Baywatch star Alexandra Paul.

In 1993, the Guinness book of world records declared the show the most watched television program in the history of humanity. With more than a billion viewers per week, it catapulted Alexandra — and, inadvertently, the almost-her version the world saw in Caroline — into a strange parallel universe of celebrity, raising whole new questions about the sisters’ separate and collective identity, in public and in private.

Beneath the personal story lurk larger inquiries about who we are as a culture, who we are as individuals, and how we come to construct and inhabit the “who” of who we are.

Reflecting on how early the constant tussle between the conflation and separation of their identities began, Paul writes:

Our twinning experience was strange right from the beginning. When my mother’s doctor heard one strong, steady heartbeat through his stethoscope back in 1963, he surmised she was cooking a vigorous, healthy baby, and not two girls whose hearts were in sync (ultrasounds were not yet in widespread use). Even when my mother went into labor six weeks early, no one suspected. It was not until Alexandra was in his hands that the doctor cried, “Hold on, Mrs. Paul, there’s another one coming!” and two minutes later I glissaded onto the table, already not wanting to be left behind. We were both well under five pounds. We were labeled Baby A and Baby B and rushed to separate incubators. We had inadvertently posed as one person for nine months, and it would be days until my parents would recover enough from the shock to name us.

[…]

We called each other by my name, Caroline, supposedly because I could not pronounce Alexandra… Early on, Alexandra was the more precocious one, I more shy. Baby photos are easily deciphered because her mouth was always open, mid-babble or laugh, while I stared at her or at the camera like a marmot caught in the beam of a flashlight, baffled and resigned. And so it was preordained: Alexandra had the makings of an actress, and I was already comfortable with the fleeting attention due a fake celebrity.

[…]

The world compared us constantly. It was easy; we had a measuring stick right next to us. Who was prettier, stronger, smarter, nicer, funnier? Naturally, I wanted to be — but not at the expense of my twin. Could I just be pretty, strong, smart, nice, funny? No. Unbidden, the first thing people did was enumerate our differences. We were seen in reference to each other, and never on our own terms.

With an eye to what she elegantly calls “the porous relationship between reality and entertainment,” Paul draws a perceptive parallel between two very different yet very similar cultural domains of identity-muddling:

The way we treat identical twins is strikingly similar to the way we treat celebrities. Our stares are naked, open, unapologetic… We conflate twins with each other, and celebrities with the characters they play on TV.

Tucked into the story are also curious and reality-warping facts about the strange science of twindom that illuminate our assumptions about the givens of being human — the wellspring of so many of our beliefs about identity. Recounting one particularly comical anecdote from their twenties, when the sisters successfully used their twindom to prank Alexandra’s director on the film set, Paul writes:

“You’re so lucky!” singletons exclaim upon hearing stories like this one. “I wish I was a twin.”

“Well,” I tell them, “Perhaps you were.”

One in 90 live births result in twins (fraternal and identical), but one in eight begin as twins. This phenomenon of “the vanishing twin” still puzzles scientists; they aren’t sure why one disappears and one remains. The “how” is only a little clearer. The best guess is that the fetus is absorbed into the mother’s body; sometimes it may be assimilated into the surviving twin. Often it happens so early that no one is the wiser. But advances in technology mean that fetuses can be tracked earlier and earlier, and it’s now clear that many humans born alone may once have had a sibling in the womb.

While the numbers are new and surprising, the vanishing twin phenomenon has been recognized for centuries. Hair and teeth were found in singletons, often much later in life. Five tiny fetuses were once discovered in the brain of a child. A six-pound fetus was removed from an elderly man. Sometimes two fraternal embryos can merge to become one body — detected when blood tests show two different blood types…

All of this is to say that 15 percent of singletons — and this is a conservative number — had a twin who disappeared sometime during pregnancy. What does this mean for the survivor? Is there a subconscious understanding that a twin was lost? Could this account for some singletons’ fascination with twins, or others’ inexplicable certainty that something is missing?

In complete contrast to the innermost identity that defines twins — one woven into the very strands of their DNA — is the identity conferred by celebrity, a judgment of personhood granted from the outside on the basis of outermost characteristics. Paul writes:

Celebrity is not an inner condition, like happiness or desperation; it is instead bestowed by the rest of us. Celebrity is not even dependent on something you consciously do; it is just, according to Merriam-Webster, the “state of being famous, celebrated.” A celebrity may be a talented soccer player/opera singer/banker. But a talented soccer player/opera star/banker is not necessarily a celebrity. The mantle is placed after an unspoken agreement between a certain number of other people.

But perhaps the greatest and most uncomfortable question of identity in the story is the subtlest, most unspoken one. Make no mistake — for all her self-effacing geniality and the generosity with which she paints her sister’s virtues of character, Caroline herself is an exceptional person: a former firefighter who spent many years as one of only fifteen women on San Francisco’s 1,500-person Fire Department, a fearless pilot who flies experimental planes, and a terrifically talented writer, author of the memoir Fighting Fire, the historical novel East Wind, Rain, and the funny and poignant micro-memoir Lost Cat, illustrated by her partner and frequent Brain Pickings collaborator Wendy MacNaughton.

Yet under the tyranny of celebrity culture, we idolize not the writer, pilot, and firefighter but the Hollywood actor; we lionize the fictional lifeguard on television while her real-life twin spends her days saving real lives from burning buildings and writing excellent books about it. Amplifying this gobsmacking inversion is the question of gender — twenty years after the heyday of Baywatch, ours remains a culture still more likely to celebrate women for being beautiful and half-naked than for being strong, selfless, and intellectually zealous.

The most paradoxical part is that although Caroline’s loving depiction renders Alexandra a kind and altogether wonderful person, these actual character qualities are utterly irrelevant in the currency of her celebrity, sold by Hollywood and bought by fans on the basis of a complete fictional projection, celebrated for the make-belief attributes of the character she portrays on TV, or even for her mere scale of her presence in millions of homes via the permeable membrane of the TV screen.

Celebrity, indeed, is a curious condition — it rarely afflicts Nobel laureates but is automatically conferred upon television stars watched by a billion viewers. This says something quite unsettling about our culture’s values and our civilizational priorities. It also asks us to examine not only the object of our stares — be it a celebrity or a pair of twins — but also the deepest values of the self behind the eyes that do the staring.

In the remainder of the thoroughly pause-giving Almost Her, many such grand questions about cultural and individual identity arise from the minute scale of Paul’s experience both as a twin and as the twin of a celebrity, from the moral and emotional ambivalences of being constantly mistaken for her famous sister to our collective contract about privacy and its culturally permissible invasions to the strangely supple pillars of personhood.

Complement it with Meghan Daum on how we become who we are, young Leo Tolstoy’s diaries of the search for a solid self, and Rebecca Goldstein on the mystery of personal identity over time.