The term “Siamese twins” comes from Chang and Eng Bunker, conjoined brothers born in 1811 in Siam (now Thailand). They were taken from their home country in 1829 and exhibited across the United States and Europe as a curiosity, and their fame was so widespread that their nationality became shorthand for the condition itself. The term stuck for nearly two centuries, though “conjoined twins” is now the preferred medical and general term.
Chang and Eng Bunker: The Original “Siamese Twins”
Chang and Eng were born connected at the chest by a band of tissue that contained shared blood vessels running between their livers. They were discovered as teenagers and brought to the U.S. in 1829, where they were displayed before audiences in a country hungry for novel entertainment. Their exhibitions eventually included appearances at P.T. Barnum’s American Museum in New York City, where they were marketed alongside other so-called “human curiosities” in what was a deeply exploitative but wildly popular form of showmanship.
Because the brothers came from Siam, promoters billed them as “The Siamese Twins.” The label was a marketing choice, not a medical one, but it caught on so completely that English speakers used it as a generic term for any conjoined twins for the next 150 years.
Their Lives Beyond the Stage
The Bunkers eventually tired of touring and settled in rural North Carolina, near Wilkesboro. They opened a general store, became naturalized U.S. citizens, and in 1843 married two sisters, Adelaide and Sarah Yates. Eng and Sarah had eleven children; Chang and Adelaide had ten. By 1846 their growing families needed more space, so the brothers built two homes nearly a mile apart in Surry County. They alternated between the houses every three days for the rest of their lives.
Their connection could not have been safely separated with 19th-century surgery. The shared blood vessels between their livers meant that cutting the band would almost certainly have killed one or both of them. Both brothers died in 1874.
Why the Term Fell Out of Use
Doctors and journalists have largely replaced “Siamese twins” with “conjoined twins” because the older term ties a medical condition to a specific ethnicity for no scientific reason. Conjoined twins occur in every population worldwide, at a rate of roughly 1.5 per 100,000 births. The condition has nothing to do with geography or nationality, so naming it after one country was always inaccurate. The shift in language also reflects a broader move away from the freak-show framing that defined how the Bunkers were presented to the public.
How Conjoined Twins Form
Conjoined twins develop when a fertilized egg begins to split into identical twins but stops before the process is complete. The point where splitting stops determines where the twins remain attached. The most common type, accounting for about 28% of cases, involves connection at both the chest and abdomen, where twins often share a liver and parts of the digestive system. Twins joined only at the chest make up about 18.5% of cases and frequently share a heart, which makes surgical separation extremely difficult.
Other types include twins joined at the abdomen (about 10%), at the skull (about 6%), at the lower spine, or side by side sharing a single torso. Each configuration presents different challenges depending on which organs are shared. Twins joined at the skull, for example, have separate brains but share bone and blood supply. Twins joined at the chest who share a heart face the most serious prognosis.
Survival and Separation
Most conjoined twins do not survive long after birth. Among those tracked in a large international study, only about 46% were born alive, with many lost during pregnancy or shortly after delivery. Surgical separation is possible in some cases but depends entirely on which structures the twins share. A shared liver can sometimes be divided. A shared heart generally cannot.
The first successful separation surgery dates back to 1689, when a Swiss surgeon named Johannes Fatio separated a pair of conjoined twin girls, Elisabet and Catherina. Separation techniques have advanced enormously since then, but the surgery remains one of the most complex procedures in medicine, often involving teams of dozens of specialists working over many hours. Success depends less on surgical skill alone and more on the specific anatomy of each pair.
A Name That Outlived Its Origin
The phrase “Siamese twins” persisted so long partly because Chang and Eng were genuinely remarkable. They lived to age 62 in an era when conjoined twins rarely survived infancy, raised 21 children between them, and built a life that went far beyond the stage persona their promoters created. Their story was so widely known that for generations, most people encountered the concept of conjoined twins only through their example. The term became a fixed phrase in English, appearing in dictionaries and casual conversation alike, long after anyone remembered why Siam had anything to do with it.