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Sibling rivalries are nothing new, but generally kids wait until they're born to start fighting each other.
A clip has gone viral, showing the two foetuses seeming to hit each other inside their mother's womb.
Their father, Mr Tao, told local press that he had filmed the video during an antenatal check late last year in the city of Yinchuan.
The 28-year-old thought it was hilarious to see his unborn daughters 'boxing with each other for a few rounds', but never thought his children were going 'to be internet stars before being born'.
Since the clip was shared online, the cheeky pair have been born and were given the nicknames 'Cherry' and 'Strawberry'.
The bizarre film has received more than 2.5 million likes and 80,000 comments since it was published on China Daily.
One viewer wrote: "Whoever wins [the fight] can be the elder one when they are born,"
while a second person added: "They fight in [their mother's] belly, but will love each other when they are born."
But according to Mr Tao, this isn't the first time the siblings had been spotted interacting. Earlier this year, he spotted the twins hugging each other during another visit to the doctors.
The loving dad said one was hugging the other while his wife was undergoing an amniotic fluid test.
He said: "We were so touched. The babies were so small and they knew how to look after each other. I believe they will live with each other in harmony when they grow up."
And according to the father, the pair shared the same amniotic sac and placenta while inside the womb. Scientifically known as monochorionic monoamniotic twins - or 'mo-mo twins' - it is one of the rarest types of pregnancy, occurring once in every 35,000 to 60,000 per year, according to TwinsUK.
It is also incredibly dangerous, with both children having their own umbilical cords meaning there is the risk they could become tangled and prevent proper blood flow.
Basically, it's one of the highest risk twin pregnancies possible. There is only a 50 percent chance that the babies will survive after 26 weeks.However, according to reports, both 'Cherry' and 'Strawberry' were born on 8 April via a caesarean section.
Deputy director from the hospital He Lin said: "The babies have been born safe and sound. It's their parents' fortune as well as my fortune. They are the first pair of Mo-Mo twins our hospital has successfully delivered."
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