Craniopagus Siamese twins

Such Siamese twins have a common head.

Dori and Lori Schapell, born around 1962. The look away from each other, as their heads are grown together at the left temple of each. They consider themselves as completely different individuals, although, of course, they cannot move independently. In fact, it is Lori, who moves. Her sister is by 10cm smaller and has to sit permanently on a sort of wheel chair. Lori works in a laundry of a hospital, and during her work Dori has to read books. Dori likes country music and goes to many concerts, accompanied necessarily by Lori. They have not always the same friends, they do not want to eat the same food. They do not even eat always at the same time. Lori would like to marry and have children.

Yvonne and Yvette McCarther, born 1949. According to Guiness this is the oldest surviving unseparated pair of Siamese twins. As Dori and Lori they have rejected surgical separation (in fact a rather difficult and dangerous operation).
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Chang and Eng Bunker (1811-1974). 

It seems that the name "Siamese" twins derives from them, they were born in Thailand by Chinese parents. Their names should mean "left" and "right". The were joined by a cartilagineous band at the chest. They married both in 1843 and had 10 and 12 children respectively. They died within three hours of each other.