diprosopus
Diprosopus is a rare, life-threatening developmental defect during embryogenesis, and a subtype of conjoined twins, characterized by partial or complete duplication of the facial structures on a single head, neck, trunk and body. It may be associated with congenital anomalies involving the central nervous, cardiovascular, gastrointestinal and respiratory systems. Cleft lip and palate have been reported in rare cases.