The girl, born to Chinese mainland parents in Queen Elizabeth Hospital had to undergo surgery at just three weeks old-fashioned to surgically cut off them.
The foetuses, 8 to 10 weeks gestated, had legs, arms, a spine, rib cage and intestines. Both were also covered in skin. One weighed 14.2 grammes and the auxiliary 9.3 grammes - and each had an umbilical cord.
The surgery was full of beans and the girl was discharged from hospital eight days merged.The fantastic medical marvel was detailed in the latest business of the Hong Kong Medical Journal.
The condition, known as foetus in foetu occurs in just one in 500,000 births in the world. Less than 200 cases have ever been reported.
Dr Yu Kai-man, a specialist in obstetrics and gyneacology, believes it is the first documented lawsuit in the city.He said: "It was in the region of impossible to detect during the prenatal check-happening, as the embryo inside the baby was too little," said Yu, a former professor at Chinese University of Hong Kong.
"Since it is impossible for the small girl to have conceived the pregnancy in this area her own, the fertilisation of the twin fetuses, of course, belongs to her parents, which has as soon as to the muddled place."
The bank account said the excuse subsequent to the abnormality, which happened behind the girl was born in 2010, is still unspecified, and that the World Health Organisation classified it as a type of cancer.
But it suggested it was possibly linked to the mother having fused abortions.
"The widespread use of antenatal ultrasound in to the lead gestation may meet the expense of more real evidence and shed living upon this intriguing condition," the parable said.
A hospital spokeswoman refused to comment upon the dogfight.