1 Language That Only 2 People Speak: The Secret Language Of Twins

Insights from the multilingual twin brothers who transformed their secret twin-speak into a constructed language.

Secret forms of communication have been around for as long as people have had secrets to keep – from the substitution ciphers used by the Romans to encrypt military intelligence to slang that can insulate a community from outsiders. But some secret codes are so esoteric that they are known by only two people and become languages unto themselves.

In the above video, Matthew and Michael Youlden warily admitted to me that they speak a “twin language” together, a secret language that only they know how to speak. “But we’re not going to talk about that, are we?” they concurred before quickly changing the subject. Ciphers, codes and slang are one thing, but a constructed language spoken by only two people on Earth piqued my curiosity and set my imagination into overdrive. What was this home-brewed, secret language? Maybe the Super Polyglot Brothers didn’t want to talk about it, but I sure did! So a colleague and I cornered Matthew last week to interrogate him on the subject (granted, it was a rather comfortable corner of an Italian restaurant in Kreuzberg, and our “interrogation” was nothing if not friendly and fuelled by genuine intrigue).

It turns out we weren’t the first people who have sought entry into the secret world of this two-person language. Matthew and Michael have had to rebuff would-be infiltrators before – like the linguist who desperately wanted to write his master’s thesis about their language. Keeping the secret remains a top priority, but Matthew agreed to answer some questions about the language while keeping its inner workings safely guarded.


Their secret language probably wouldn’t have developed at all if the brothers hadn’t been twins. It turns out that “twin languages” are not an unusual occurrence. The phenomenon, also called cryptophasia (Greek: “secret” + “speech”), describes a language developed by twins in early childhood which they only speak with each other. Invented languages spoken by very few people are also referred to as autonomous languages or idioglossia.

Most young people develop at least a few code and slang words to communicate secretly under adults’ noses, even if it’s as simple as calling the secret make-out spot “the library”. However, because twins spend so much time together from birth, and because their mental and linguistic development is so in sync, they are especially likely to invent their own language to the exclusion of everyone – parents and peers alike. Cryptophasia is thought to occur among almost 50% of twins (both identical and fraternal).

Under heavier scrutiny, most cryptophasia is revealed to be toddlers’ mispronunciation of their mother tongue – a phase that every child goes through. However, because twins can understand each other when no one else can, these mistakes are more likely to get reinforced while the mother tongue flows around them. In very rare cases, like that of the Kennedy Sisters in the 1970s, a twin language can flourish while fluency in the mother tongue never develops properly.

Poto and Cabengo

Grace and Virginia Kennedy (or Poto and Cabengo, as they called each other) grew up in San Diego, CA in the 1970s. By the age of six they still couldn’t speak English, but instead conversed in a seemingly elaborate and nuanced tongue that no one else could understand. By age six, their exasperated parents sought professional help. Their discovery caused a worldwide media sensation and prompted headlines like, “Twin girls invent own language”.

Linguists became fascinated by these little savants, and, like anthropologists studying an indigenous culture, several went about trying to discover the rules of the language and gain entry into Poto and Cabengo’s two-person society. But after thoroughly studying the twins, the evidence revealed a different story: two very isolated children who suffered from lack of mental stimulation and social contact. Misdiagnosed in infancy as mentally disabled (they were later found to have average IQs), they were never enrolled in school and rarely left the house. They spent very little time with their parents and were mostly raised by their grandmother, who spoke to them seldomly and then only in German. Lacking adult attention, peers, or even knowledge of the outside world, Grace and Virginia’s invented language filled a significant void.

Researchers finally concluded that their seemingly ingenious constructed language was little more than a hodge-podge of English and German words that lacked consistent pronunciation, syntax and grammar. With the help of speech therapists, the girls did eventually learn to speak English, but never well enough to catch up with other kids their age or fully integrate into society.

Thankfully, most twins are spared this tragic outcome because they receive enough exposure to their native language for it to quickly override their twin-speak. A twin language lacks the complexity to function in the outside world so most cryptophasic twins tend to abandon their secret language around the age of three. But can a twin language, an inside joke born from babble, grow beyond the childhood bedroom and develop into a truly functional language?


That’s where Matthew and Michael Youlden return to the story. Instead of abandoning their twin-speak in early childhood (like most twins do), or continuing to speak it to the detriment of their own native tongues (like the Kennedy sisters), they made it their hobby to start developing their cryptophasia into a truly functional language with a lexicon, written alphabet and grammar. According to Matthew, “I guess we would have been about 6 or 7 when we actively started to become conscious about it and ‘shape’ it into an almost normal, standardized language.” They called the language Umeri, and they’re still working on it.

Although they are unwilling to reveal too much, Matthew assured us that, after more than twenty years of adding and tinkering, Umeri has graduated far beyond its cryptophasic origins into a coherent language – one that, hypothetically, anyone could learn. As the only speakers of Umeri, as well as its only authorities, the language evolves through collaboration and consensus. They created a completely original alphabet which allowed them to write words made from phonemes that don’t exist in English or Irish (their two native languages), although a recent language reform managed to reconcile their script with the Latin alphabet enough to be able to type Umeri. They are constantly updating the Umeri dictionary to keep track of the thousands of words they’ve added over the years to keep the language current and useful. Adding to the lexicon has a straightforward process: if one twin can’t understand a neologism introduced by the other, it probably won’t be adopted. The brothers have also developed thorough grammar rules. For example: all plurals end in “i” and there’s even a genitive case! Amazingly, some of their verbs are even irregular, which suggests that in some fundamental way there’s no escaping them, even when you invent your own language.

Realizing just how much they’ve invested in Umeri over the years I had to know if it would be worth keeping the language secret if it meant it died with them. Was there a temptation to record it for posterity or pass it on? Several generations down the line, might there be a small community of Umeri speakers holding their own, like the speakers of Boontling in Northern California? The twins are resolute on this issue:


“It would be a real shame to think that, when we go, the language also goes with us, which is unfortunately a common dilemma faced by many languages and speakers throughout the world. We’ve thought about it a lot which is why we decided to document it. That said, as much as we regard it as a “real” and living language, it’s also only our language and, as fun as it would be to pass it on, there’s also this feeling that it has an expiry date. When we go, it goes with us. And everyone else can read about it!”

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