Siamese twins

Siamese twins Identical (monozygotic) twins that do not separate fully from one another but remain partially united due to the incomplete division of one fertilized ovum. Such twins are known medically as conjoined twins. Conjoined twins are popularly known as Siamese twins after Chang and Eng, the celebrated conjoined Chinese twins born in Siam (Thailand) in the early 19th century. Depending on the anatomy of the union, surgical procedures can be done that separate conjoined twins.