When Xiao Feng’s parents brought him to the hospital, they were concerned that he was having difficulty breathing and abdominal swelling. They could not have possibly expected what doctors found after extensive testing: Feng’s undeveloped twin was inside his stomach, and he had to have an operation to “give birth” to the fetus.

Feng was diagnosed with a rare case of cryptodidymus. Cryptodidymus is a term that describes conjoined twins, one of whom is concealed in a part of the other's body. These cases are extremely rare, characterized by a poorly developed “parasitic twin,” which is pretty much still a medical anomaly. According to Metro, a conjoined twin can only survive as a parasite if it is not inside the other twin.

In Feng’s case, the twin growing inside of him took up about two-thirds of his stomach. It had grown to be about 10 inches. It also developed a spine, fingers, and toes.

Watch Xiao Feng’s story below: