Twins bring twice the happiness to their parents. They can also bring twice the headache.
A pair of identical twin sisters have been spotted apparently fighting with each other while they were still in their mother's womb.
In the trending video from China, the two foetuses were seemingly kicking and hitting each other as their mother underwent an ultrasound scan at four months pregnant.
The twins' father, 28-year-old Mr Tao, said the footage was filmed by him when he accompanied his wife to an antenatal check late last year in the city of Yinchuan.
Mr Tao told Chinese news outlet The Paper that he found it amusing to see his unborn daughters seemingly 'boxing with each other for a few rounds'.
He filmed the ultrasound footage before uploading it to short-video app Douyin. The video quickly went viral.
Mr Tao said he hadn't expected his girls 'to be internet stars before being born'.
The naughty girls have been born healthy and were given the nicknames 'Cherry' and 'Strawberry' - after their mother's favourite fruits.
The footage has so far received more than 2.5 million likes and 80,000 comments.
It has also been widely shared by Chinese news outlets, such as China Daily.
One amused viewer joked on Douyin: 'Whoever wins [the fight] can be the elder one when they are born.'
Another one noted: 'They fight in [their mother's] belly, but will love each other when they are born'.
Mr Tao added that he saw his twin daughters hugging each other during another check in January.
He said he saw one of them apparently cuddling the other when his wife was going through an amniotic fluid test.
'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,' Mr Tao told The Paper.
According to the father, his daughters shared the same amniotic sac as well as placenta inside his wife.
Known as monochorionic monoamniotic twins or Mo-Mo twins, it's one of the highest risk twin pregnancies possible. There is only a 50 per cent chance that the babies will survive after the 26 week mark.
The biggest risk with this pregnancy is that the umbilical cords - which are separate - will get tangled and knotted resulting in impaired blood flow to one or both of the babies.
Mo-Mo twins are rare and occur in approximately 1 in 35,000 to 1 in 60,000 pregnancies, according to TwinsUK.
Fortunately, 'Cherry' and 'Strawberry' were born healthy on April 8 at 32 weeks via a caesarean section.
The elder sibling was born at 2:51pm, weighing 1,950 grams (4lb 5oz) and the younger one was born one minute later weighing 1,620 grams (3lb 9oz), reported Yangzhou Evening News.
Doctors at the General Hospital of Ningxia Medical University said emergency surgery was arranged after nurses saw one of the twins' heart rate had suddenly dropped.
During the operation, they found a large portion of their umbilical cords had got tangled.
He Lin, a deputy director at the hospital's obstetrical department, told reporters: '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.'
© Associated Newspapers Ltd.