A few years back, there was a crying woman on the bathroom floor. She wasn't crying out of sadness; no, those thick tears leaving her eyes emphasized joy. In her hands she was holding a pregnancy test. Two red pluses. She was pregnant.
All her life she wanted nothing more than giving birth to a beautiful child, raising it and showering it with love.
Her husband, a man in his early thirties, was trying his best to hold his tears back. Just like his wife, he always had wanted a child. Preferable a boy, someone who would grow strong and could take over his business.
The Chinese-Korean family was poor. Zhoumi didn't want to do to college, but started his own business selling fish. His parents just had enough money to barely survive the day. Going to college would have been their end, having to give all their money to their son. They said it was okay, but Zhoumi knew better.
Krystal, a Korean woman in her late twenties came from a rather wealthy family. They weren't rich though, just had enough to live a happy life. As she left with a man whose been poor all his life long tho, her parents stopped supporting her.
When Krystal reached the legal age, 21, she left her home and began a new life in China. Zhoumi found her when she was dirt-broken living on the streets and took her with him to his parents house, letting her live with the three. 
It didn't take long for them to fall in love and marry. Sharing many hobbies and interests they clicked from the beginning on. They both lived with Zhoumi's parents until the elders died. It was a sad event, but doesn't have much importance for this story.
The nine months of pregnancy flew by like nothing. Krystal was good at handling the occasional pain and the morning sickness; she didn't have and weird cravings nor did she make her husband's life a living hell like you see in movies or read in books.
D-Day came fast. The couple drove to the hospital fast as Krystal felt her water having broke. Zhoumi stayed by her side the whole the whole time, squeezing her hands and making the nurse in the room laugh softly as Krystal made a joke about her having to be the scared one, not him. 
Everything was going well until Krystal suddenly started screaming in pain. Zhoumi's eyes widened and he ordered, no, demanded the doctor to do something, to help his wife, to take the pain away. And the doctor tried his best. Two nurses held her down and they immediately started with the giving birth process. Krystal tried to follow the doctor's orders, but she was weak and kept screaming and crying, the pain having been unbearable.

Few hours later there was nothing heard but soft crying and a remorseful 'I'm sorry'. 

Krystal died as she have birth to two babies. Of course the couple was told that it would be twins, but they weren't informed that the little ones would be Siamese. 
Zhoumi cried for his wife, the tears not stopping to fall down his cheeks, but as he took a look at the newborns for the first time stopped crying for a second. Despite their state, which would have caused many parents to give he kids up for adoption, he loved them. They were beautiful in his eyes, not crying too much so it gives you a headache, not too little to make you worry that something is wrong with them.
The doctor checked them up, bringing them to another room for a few hours, which Zhoumi spend with more tears and soft 'thank you's to his deceased wide. When the doctor came back his face had the same expression as just hours before, the only difference was the sad smile he wore now. The spoken words leaving the doctor's lips bone the Chinese man's heart once again.
The babies are healthy, both will live.
But Luhan and Sehun only had one heart connecting them..