Conjoined twins

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Conjoined twins
Conjoined X-ray.jpg
X-ray of joined twins, cephalothoracopagus.
Classification and external resources
Specialty Lua error in Module:Wikidata at line 446: attempt to index field 'wikibase' (a nil value).
ICD-10 O33.7, Q89.4
ICD-9-CM 678.1, 759.4
DiseasesDB 34474
eMedicine ped/2936
Patient UK Conjoined twins
MeSH D014428
[[[d:Lua error in Module:Wikidata at line 863: attempt to index field 'wikibase' (a nil value).|edit on Wikidata]]]

Conjoined twins are identical twins[1] joined in utero. An extremely rare phenomenon, the occurrence is estimated to range from 1 in 49,000 births to 1 in 189,000 births, with a somewhat higher incidence in Southeast Asia, Africa and Brazil.[2] Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1. Most stillborns are male.[2][3]

Two contradicting theories exist to explain the origins of conjoined twins. The more generally accepted theory is fission, in which the fertilized egg splits partially.[4] The other theory, no longer believed to be the basis of conjoined twinning,[4] is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find like-stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac, although these characteristics are not exclusive to conjoined twins as there are some monozygotic but non-conjoined twins that also share these structures in utero.[5]

The most famous pair of conjoined twins was Chang and Eng Bunker (Thai: อิน-จัน, In-Chan) (1811–1874), Thai brothers born in Siam, now Thailand. They travelled with P.T. Barnum's circus for many years and were labeled as the Siamese Twins. Chang and Eng were joined by a band of flesh, cartilage, and their fused livers at the torso. In modern times, they could have been easily separated.[6] Due to the brothers' fame and the rarity of the condition, the term "Siamese twins" came to be used as a synonym for conjoined twins.[7]

Types of conjoined twins

Conjoined twins are typically classified by the point at which their bodies are joined. The most common types of conjoined twins are:

  • Thoraco-omphalopagus (28% of cases):[4] Two bodies fused from the upper chest to the lower chest. These twins usually share a heart, and may also share the liver or part of the digestive system.[8]
  • Thoracopagus (18.5%):[4] Two bodies fused from the upper thorax to lower belly. The heart is always involved in these cases.[8] As of 2015, separation of a genuinely shared heart has not offered survival to two twins; a designated twin may survive if allotted the heart, sacrificing the other twin.
  • Omphalopagus (10%):[4] Two bodies fused at the lower abdomen. Unlike thoracopagus, the heart is never involved in these cases; however, the twins often share a liver, digestive system, diaphragm and other organs.[8]
  • Parasitic twins (10%):[4] Twins that are asymmetrically conjoined, resulting in one twin that is small, less formed, and dependent on the larger twin for survival.
  • Craniopagus (6%):[4] Fused skulls, but separate bodies. These twins can be conjoined at the back of the head, the front of the head, or the side of the head, but not on the face or the base of the skull.[8]

Other less-common types of conjoined twins include:

  • Cephalopagus: Two faces on opposite sides of a single, conjoined head; the upper portion of the body is fused while the bottom portions are separate. These twins generally cannot survive due to severe malformations of the brain. Also known as janiceps (after the two-faced god Janus) or syncephalus.[8]
  • Syncephalus: One head with a single face but four ears, and two bodies.[8]
  • Cephalothoracopagus: Bodies fused in the head and thorax. In this type of twins, there are two faces facing in opposite directions, or sometimes a single face and an enlarged skull.[8][9]
  • Xiphopagus: Two bodies fused in the xiphoid cartilage, which is approximately from the navel to the lower breastbone. These twins almost never share any vital organs, with the exception of the liver.[8] A famous example is Chang and Eng Bunker.
  • Ischiopagus: Fused lower half of the two bodies, with spines conjoined end-to-end at a 180° angle. These twins have four arms; two, three or four legs; and typically one external set of genitalia and anus.[8]
  • Omphalo-Ischiopagus: Fused in a similar fashion as ischiopagus twins, but facing each other with a joined abdomen akin to omphalopagus. These twins have four arms, and two, three, or four legs.[8]
  • Parapagus: Fused side-by-side with a shared pelvis. Twins that are dithoracic parapagus are fused at the abdomen and pelvis, but not the thorax. Twins that are diprosopic parapagus have one trunk and two faces. Twins that are dicephalic parapagus are dicephalic, and have two (dibrachius), three (tribrachius), or four (tetrabrachius) arms.[8]
  • Craniopagus parasiticus: Like craniopagus, but with a second bodiless head attached to the dominant head.
  • Pygopagus (Iliopagus): Two bodies joined at the pelvis.[8]
  • Rachipagus: Twins joined along the dorsal aspect (back) of their bodies, with fusion of the vertebral arches and the soft tissue from the head to the buttocks[10]


Surgery to separate conjoined twins may range from very easy to very hard, depending on the point of attachment and the internal parts that are shared. Most cases of separation are extremely risky and life-threatening. In many cases, the surgery results in the death of one or both of the twins, particularly if they are joined at the head or share a vital organ. This makes the ethics of surgical separation, where the twins can survive if not separated, contentious. Alice Dreger of Northwestern University found the quality of life of twins who remain conjoined to be higher than is commonly supposed.[11] Lori and George Schappell and Abby and Brittany Hensel are notable examples.

In 1955, neurosurgeon Harold Voris and his team at Mercy Hospital and Medical Center in Chicago performed the first successful operation that separated Siamese twins conjoined (Craniopagus twins) at the head which resulted in long-term survival for both.[12][13][14] The larger girl was reported in 1963 as developing normally, but the smaller was permanently impaired.[15]

In 1957, Bertram Katz and his surgical team made international medical history performing the world's first successful separation of conjoined twins sharing a vital organ.[16] Omphalopagus twins John Nelson and James Edward Freeman (Johnny and Jimmy) were born to Mr. and Mrs. William Freeman of Youngstown, Ohio, on April 27, 1956. The boys shared a liver but had separate hearts and were successfully separated at North Side Hospital in Youngstown, Ohio by Bertram Katz. The operation was funded by the Ohio Crippled Children's Service Society.[17]

Recent successful separations of conjoined twins include that of the separation of Ganga & Jamuna Shreshta in 2001, who were born in Kathmandu, Nepal, in 2000. The 197-hour surgery on the pair of craniopagus twins was a landmark one which took place in Singapore; the team was led by neurosurgeons Chumpon Chan and Keith Goh.[18] The surgery left Ganga with brain damage and Jamuna unable to walk. Seven years later, Ganga Shrestha died at the Model Hospital in Kathmandu in July 2009, at the age of 8, three days after being admitted for treatment of a severe chest infection.[19]

A case of particular interest was that of infants Rose and Grace ("Mary" and "Jodie") Attard, conjoined twins from Malta who were separated in Great Britain by court order Re A (Children) (Conjoined Twins: Surgical Separation) over the religious objections of their parents, Michaelangelo and Rina Attard. The surgery took place in November, 2000, at St Mary's Hospital in Manchester. The operation was controversial because Rose, the weaker twin, would die as a result of the procedure as her heart and lungs were dependent upon Grace's. (The twins were attached at the lower abdomen and spine.) However, if the operation had not taken place, it was certain that both twins would die.[20][21] Grace survived to enjoy a normal childhood.[22]

In 2003 two 29-year-old women from Iran, Ladan and Laleh Bijani, who were joined at the head but had separate brains (craniopagus) were surgically separated in Singapore, despite surgeons' warnings that the operation could be fatal to one or both. Their complex case was accepted only because high tech graphical imagery and modelling would allow the medical team to plan the risky surgery. Unfortunately, an undetected major vein hidden from the scans was discovered during the operation.[23] The separation was completed but both women died while still in surgery on July 8, 2003.

Conjoined twins in history

Conjoined brothers from Nuremberg Chronicle (1493).
Conjoined twin sisters from Nuremberg Chronicle (1493).
Moche ceramics depicting conjoined twins. 300 CE Larco Museum Collection Lima, Peru.

The Moche culture of ancient Peru depicted conjoined twins in their ceramics dating back to 300 CE.[24] Writing around 415CE, St. Augustine of Hippo in his book City of God refers to a man "double in his upper, but single in his lower half--having two heads, two chests, four hands, but one body and two feet like an ordinary man."[25] The earliest known documented case of conjoined twins dates from the year 942, when a pair of conjoined twin brothers from Armenia were brought to Constantinople for medical evaluation.

In Arabia, the twin brothers Hashim ibn Abd Manaf and 'Abd Shams were born with Hashim's leg attached to his twin brother's head. Legend says that their father, Abd Manaf ibn Qusai, separated his conjoined sons with a sword and that some priests believed that the blood that had flowed between them signified wars between their progeny (confrontations did occur between Banu al'Abbas and Banu Ummaya ibn 'Abd Shams in the year 750 AH).[26] The Muslim polymath Abū al-Rayhān al-Bīrūnī described Siamese twins in his book Kitab-al-Saidana.[27]

The English twin sisters Mary and Eliza Chulkhurst, who were conjoined at the back (pygopagus), lived from 1100 to 1134 (or 1500 to 1534) and were perhaps the best-known early historical example of conjoined twins. Other early conjoined twins to attain notice were the "Scottish brothers", allegedly of the dicephalus type, essentially two heads sharing the same body (1460–1488, although the dates vary); the pygopagus Helen and Judith of Szőny, Hungary (1701–1723), who enjoyed a brief career in music before being sent to live in a convent; and Rita and Cristina of Parodi of Sardinia, born in 1829. Rita and Cristina were dicephalus tetrabrachius (one body with four arms) twins and although they died at only eight months of age, they gained much attention as a curiosity when their parents exhibited them in Paris.

Grave of Eng and Chang Bunker near Mt. Airy, North Carolina

Several sets of conjoined twins lived during the nineteenth century and made careers for themselves in the performing arts, though none achieved quite the same level of fame and fortune as Chang and Eng. Most notably, Millie and Christine McCoy (or McKoy), pygopagus twins, were born into slavery in North Carolina in 1851. They were sold to a showman, J.P. Smith, at birth, but were soon kidnapped by a rival showman. The kidnapper fled to England but was thwarted because England had already banned slavery. Smith traveled to England to collect the girls and brought with him their mother, Monimia, from whom they had been separated. He and his wife provided the twins with an education and taught them to speak five languages, play music, and sing. For the rest of the century the twins enjoyed a successful career as "The Two-Headed Nightingale" and appeared with the Barnum Circus. In 1912 they died of tuberculosis, 17 hours apart.

Giovanni and Giacomo Tocci, from Locana, Italy, were immortalized in Mark Twain's short story "Those Extraordinary Twins" as fictitious twins Angelo and Luigi. The Toccis, born in 1877, were dicephalus tetrabrachius twins, having one body with two legs, two heads, and four arms. From birth they were forced by their parents to perform and never learned to walk, as each twin controlled one leg (in modern times physical therapy allows twins like the Toccis to learn to walk on their own). They are said to have disliked show business. In 1886, after touring the United States, the twins returned to Europe with their family, where they fell very ill. They are believed to have died around this time, though some sources claim they survived until 1940, living in seclusion in Italy.

List of notable conjoined twins

Names listed in boldface are of twins who have been separated.

Born 19th century and earlier

Chang and Eng Bunker, watercolor on ivory, 1835 or 1836

Born 20th century

Born 21st century

Conjoined twins lambs Former collection : Naturalization and collection Jules Berdoulat last quarter of the nineteenth century. Size : 66 x 37.5 x30 cm
  • Carmen and Lupita Andrade-Solis, born in Mexico in 2000 with Dicephalus Tetrabrachius Dipus (2 heads, 4 arms and 2 legs). Separation was not possible.
  • Carl and Clarence Aguirre, born vertical craniopagus in Manila on 21 April 2002, successfully separated in 2004.[30]
  • Kendra and Maliyah Herrin, ischiopagus twins separated in 2006 at age 4.[31]
  • Anastasia and Tatiana Dogaru, born outside Rome, Italy on January 13, 2004. As Craniopagus twins, the top of Tatiana's head is attached to the back of Anastasias's head.
  • Lakshmi Tatma (born 2005) was an ischiopagus conjoined twin born in Araria district in the state of Bihar, India. She had four arms and four legs, resulting from a joining at the pelvis with a headless undeveloped parasitic twin.[32]
  • Vani and Veena (Warangal, Telangana state, India) craniopagus twins, attached at the back of the skull.
  • Krista and Tatiana Hogan, Canadian twins conjoined at the head. Born October 25, 2006. Share part of their brain and can pass sensory information and thoughts between each other.
  • Trishna and Krishna from Bangladesh were born in December, 2006, Craniopagus twins, joined on the tops of their skulls, and sharing a small amount of brain tissue. In 2009, they were separated in Melbourne, Australia.[33]
  • Marek and Michal Müller, born in April 2007 in Slovakia. Conjoined by the stomach and chest. In September 2007, they were separated in Bratislava. They both died after surgery. Marek in October and Michal in November 2007.
  • Maria and Teresa Tapia, born in the Dominican Republic on April 8, 2010. Conjoined by the liver, pancreas, and a small portion of their small intestine. Separation occurred on November 7, 2011.
  • Emma and Taylor Bailey, thoracopagus twins born in Arizona, USA in 2006. Joined at the chest and sharing a 7-chamber heart and liver. Both died during a preparatory heart surgery August 10, 2010 at age 3 in Seattle, USA.
  • Rital and Ritaj Gaboura, had been born in Khartoum, Sudan in 2010 before they were separated in London in 2011. They were craniopagus joined by tops of their heads.
  • Unnamed boy twins, born in Nakuru, Kenya in May 2013. Sharing most organs, including heart, liver, two legs, 3 visible arms, and one set of sexual organs. Separate heads. Died after 5 days.
  • Unnamed boy Dicephalic Parapagus twins, born in Jaipur, Rajasthan, India in July 2013 . The boys' heads, nervous systems and backbones are separate. The backbones are joined below the pelvis and they share a rib cage and shoulder girdle. Died after six days.[34]
  • Emmett and Owen Ezell, thoracic-omphalopagus twins, were born on July 15, 2013 and successfully separated on August 24, 2013.
  • Ousainatou and Hasanatou Jallow, thoracopagus twins born in Serrekunda in Gambia on the 6th of August 2008 to one Ramatoulie Jallow. They lived for eight days.
  • Tinashe and Tinotenda Mufuka, omphalopagus twins born in Chiweshe in Zimbabwe in July 2003. Dr. Jacob Langer of SickKids Hospital successfully separated them at about nine months of age.[35]
  • Unknown names, joined at chest and abdomen, born in Tsholotsho Zimbabwe in 2009. They died after transfer to Mpilo Central Hospital during the first month of life.[36]
  • Kupakwashe and Tapiwanashe Chitiyo, omphalopagus twins born in Murehwa in Zimbabwe in April 2014. They were successfully separated at two months of age by a team led by Dr. Bothwell Mbuwayesango.[37]
  • Knatalye and Adeline Mata, born in Texas, United States of America at Texas Children's Hospital in April 2014; they shared the lining of the heart, diaphragm, liver, intestines and pelvis. They successfully separated at the Texas Children's Hospital in a twenty six hour surgery on Feb 17, 2015 [38]

In fiction

  • Tamil actor Suriya portrays conjoined twins in the 2012 film, Maattrraan.
  • Actress Sarah Paulson portrays Bette and Dot Tattler, conjoined twins, in the fourth installment of the American Horror Story anthology series.[citation needed]
  • The film Stuck on You depicts Bob and Walt Tenor, conjoined twins portrayed by Matt Damon and Greg Kinnear. 2003.
  • CatDog depicts Cat and Dog, a hybrid of a dog and cat who are brothers.
  • Dragon Tales, a children's show which depicts Zak and Wheezie, a two-headed dragon that are brother and sister.
  • South Park features Nurse Gollum with a fetus on her head.
  • The Simpsons features Hugo in Treehouse of Horror VII, who is Bart Simpson's conjoined twin. They were separated at birth by Dr. Hibbert, and Hugo was imprisoned in the Simpsons' attic.
  • The Oblongs, depicts Biff Oblong (Randy Sklar) and Chip Oblong (Jason Sklar) – 17-year-old conjoined twins who are attached at the waist and share a middle leg.
  • In the episode "Humbug" of The X-Files, Vincent Schiavelli portrayed a circus performer named Lanny, with an underdeveloped conjoined twin named Leonard. The episode also includes a reference to Chang and Eng.
  • The Prophet of Yonwood has a reference to the Chang and Eng when the main character, Nickie, finds a picture of them in her great-grandfather's old house in Siam.
  • The film Big Fish has a reference to the North Korean twins singers, who were mentioned in one of the stories told by the main character.
  • Brothers of the Head by Brian Aldiss has two meanings: The blighted beach area where these conjoined twins, Barry & Tommy Howe, live, and the malformed, rudimentary third head that they have. The two enter the world of rock, sex -and drugs. When the third head wakes up, horror ensues.
  • In the anime Naruto, Sakon (左近) and his conjoined twin brother Ukon (右近), are the strongest of the Sound Four and count as one member due to their abilities to merge bodies and kill an opponent at a cellular level. They both serve as antagonists.
  • The Broadway musical Side Show depicts the lives of real-life conjoined twins Daisy and Violet Hilton, portrayed in the original Broadway production by Alice Ripley and Emily Skinner.
  • The American medical drama Grey's Anatomy featured several cases of conjoined twins.

See also


  1. "Conjoined Twins Facts". University of Maryland Medical Center. Retrieved 6 Jan 2012.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. 2.0 2.1 "Clinics - Importance of angiographic study in preoperative planning of conjoined twins: case report". 1990-01-06. Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. "Conjoined Twins". Medscape. Retrieved 22 Oct 2015.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles> (this article includes post-mortem images)
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 "The embryology of conjoined twins (Aug. 2004)". Child's Nervous System. 20 (8–9): 508–525. Aug 2004. doi:10.1007/s00381-004-0985-4. PMID 15278382. Retrieved 22 Oct 2015.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  5. Le, Tao; Bhushan, Vikas; Vasan, Neil (2010). First Aid for the USMLE Step 1: 2010 20th Anniversary Edition. USA: The McGraw-Hill Companies, Inc. p. 121. ISBN 978-0-07-163340-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. "h2g2 - Twins - A369434". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  7. "Conjoined Twins". University of Maryland Medical Center. January 8, 2010. Retrieved February 9, 2010.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  8. 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 8.11 [1] Archived February 15, 2012 at the Wayback Machine
  9. "". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  10. Spencer, R (1995). "Rachipagus conjoined twins: They really do occur!". Teratology. 52 (6): 346–56. doi:10.1002/tera.1420520605. PMID 8711621.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  11. "One of Us: Conjoined Twins and the Future of Normal: Alice Domurat Dreger: 9780674018259: Books". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. "The craniopagus malformation: classification and implications for surgical separation". Oxford University Press. April 5, 2006. Retrieved October 14, 2015. Cite journal requires |journal= (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  13. "Mercy Firsts". Retrieved October 14, 2015.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  14. "Seaparate Siamese Twins!". Chicago Tribune. April 22, 1955. Retrieved October 14, 2015.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  15. Voris, Harold C. (February 1963). "Cranioplasty in a Craniopagus Twin". Journal of Neurosurgery. 20 (2): 145–147. doi:10.3171/jns.1963.20.2.0145.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  16. "Dr. Bewrtram Katz, 83 - Obituary". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  17. [2][dead link]
  18. "In Conversation with Medicine's Miracle Workers -- Dr Chumpon Chan and Dr Keith Goh". Channel News Asia Singapore. April 19, 2001. Retrieved March 27, 2010.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  19. [3] Archived November 5, 2013 at the Wayback Machine
  20. "Siamese twin Jodie 'to go home soon'". BBC News. April 23, 2001. Retrieved March 27, 2010.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  21. Appel, Jacob M. Ethics: English high court orders separation of conjoined twins. Journal of Law Medicine & Ethics. 2000 Fall;28(3):312-3.
  22. "We don't know how to tell Gracie her sister died so she could live; EXCLUSIVE DILEMMA FACING TWINS' PARENTS DAILY Mirror BEST FOR REAL LIFE. - Free Online Library". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  23. "Wired 11.10: Till Death Do Us Part". 2001-04-11. Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  24. Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
  25. "CHURCH FATHERS: City of God, Book XVI (St. Augustine)". Retrieved 2014-08-03. |chapter= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  26. The Life of the Prophet Muhammad: Al-Sira Al-Nabawiyya By Ibn Kathir, Trevor Le Gassick, Muneer Fareed, pg. 132
  27. A. Zahoor (1997), Abu Raihan Muhammad al-Biruni, Hasanuddin University.
  28. Bondeson, Jan (April 1992), "The Biddenden Maids: a curious chapter in the history of conjoined twins", Journal of the Royal Society of Medicine, London: Royal Society of Medicine Press, 85 (4): 217–221, PMC 1294728, PMID 1433064CS1 maint: ref=harv (link)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  29. "Sláva i utrpení sester srostlých v pánvi –". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  30. DA Staffenberg and JT Goodrich. Separation of craniopagus conjoined twins: an evolution in thought. Clin Plast Surg. 2005 Jan;32(1):25-34.
  31. "Herrintwins". Herrintwins. Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  32. "Many-limbed India girl in surgery". BBC News. 2007-11-06.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  33. "NOVA | Separating Twins". Retrieved 2014-08-03.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  34. "Conjoined twins lose battle for survival - The Times of India". The Times Of India.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  35. Foss, Krista. "Miracle at Sick Kids", UofT Magazine, Toronto, Summer 2005. Retrieved on 20 August 2014.
  36. Whiz, Lindie. "Pictures: Local surgeons separate Siamese twins", NewZimbabwean, Harare, 21 April 2009. Retrieved on 20 August 2014.
  37. Nleya, Feluna. "Pictures: Local surgeons separate Siamese twins", NewsDay, Harare, 9 July 2014. Retrieved on 20 August 2014.
  38. . "Doctors share more good news on separation of conjoined twins", KHOU, United States, 24 February 2015. Retrieved on 24 February 2015.

External links