The wonders of reproductive biology...
ISLAMABAD, Pakistan - Surgeons operated on a 2-month-old Pakistani girl Tuesday to remove two fetuses that had grown inside her while she was still in her mother's womb, a doctor said.
Abbasi, the chief doctor who led the operation, said the case was the first he was aware of in Pakistan of fetus-in-fetu, where a fetus has grown inside another in the womb.
Linky link If you really want to be grossed out do a Google image search on fetus in fetu. Ewww.