Just about everyone is familiar with Chang and Eng as they are by far the most famous of all Siamese twins, but there's still probably plenty of information you didn't know about these two brothers. For example, the term "Siamese twins" was actually based on them. There's also a chance you know someone related to them:
The twins adopted the last name Bunker, bought a plantation and slaves, and married two sisters, Adelaide Yates and Sarah Anne Yates. Chang had 10 children, Eng 11 or 12, and today the twins’ descendants are said to number more than 1,500, among them sets of non-conjoined twins.
Learn more about the brothers and about 6 other pairs of conjoined twins over at Environmental Graffiti.