Disprosopia

Also known as craniofacial duplication is a rare disorder in which the same person's face is duplicated on its head. This is not any kind of twinning as "fetus in fetu" below. The condition is caused by a protein responsible for determining the characteristics of the face and excess leads to a second mirror face. Lack of the protein leads to underdeveloped facial features. Usually this type of anomaly even allows the child is born alive, but Lali Singh, born in 2008, survived for two months before he suffered a cardiac arrest.
Occurrences
Diprosopus often occurs in combination with other congenital diseases, particularly anencephaly, neural tube defects and cardiac malformations. When present, the brain can display abnormalities ranging from partial to complete duplication of brain structures, and / or underdevelopment of the brain tissue.
Few two-faced animals have survived due to associated internal organ abnormalities and brain abnormalities. One of the most famous was Ditto the pig. Ditto was raised to adulthood, but died of pneumonia caused by inhaling food while breathing through a muzzle while eating with the other.
Cats with the condition are known as 'Janus cats', after the Roman god. In July 2006, a 6 year old male cat named Janus "Frank and Louie" from Millbury, Massachusetts USA received publicity. In your case, only one esophagus (and possibly only one trachea) was functional and this assisted survival. In September 2011, when Frank and Louie was 12, it was announced that he will appear in the Guinness Book of World Records 2012 as the cat Janus most enduring in history.
With more human babies are stillborn diprosopus. Known cases of humans with diprosopus survivors for over minutes to hours after birth are very rare, only a few are recorded. In 2002 and 2003, two children living males with partial diprosopus been described in the medical literature for reports of separate cases. A baby born with duplication of the nose and the frontal brain lobes, two widely spaced eyes, a small, underdeveloped central orbit, and a big mouth and asymmetric. The other child was born with duplication of the upper and lower jaw, ending two languages ​​in the same database, cleft palate, a hint of slightly broken nose and two eyes widely spaced, as well as absence of the corpus callosum, duplication of the gland and pituitary stalk, and abnormalities in the midbrain. Because they were born with a milder form, partial diprosopus, both children were considered candidates to correct their abnormal facial features.