In 1939, a man from a small village in the Andes mountains carried his five-year-old daughter Lina into a hospital in the town of Pisco, Peru. He indicated to the doctors there that the shamans in his village had been unable to cure the large tumor that was developing in her abdomen. Upon examination, the doctors learned that the swelling was not actually a tumor.
Dr. Gérado Lozada was told by Lina's father that she had been having regular periods since age three, but they had stopped about 7 1/2 months prior to the visit. He listened to the young girl's abdomen with a stethoscope, and heart a tiny second heartbeat. An X-Ray was also performed, after which there could be no doubt… to the doctors' astonishment, five-year-old Lina Medina was about seven months pregnant.
Sadly, the identity of the father was never established. Who on earth...I just don't understand people sometimes. Someone had to have sex with this girl for her to be carrying a child. She was five! What is wrong with people?!
Lina's father was temporarily jailed on suspicion of incest, but he was released for a lack of evidence and authorities were never able to determine who fathered Lina's child.Source.
After the baby was a couple years old a follow up investigation revealed that the family was raising the child as Lina's little brother and he did not know the truth until around the age of 10, when a group of schoolmates taunted him with the truth.