For any parents, losing a child is a devastating experience. In China, the loss comes even more tragic because of its decades long one-child policy.

　　For about 40 years, each Chinese couple was only allowed to have one child. And for those who lost their only son or daughter, life could be lonely, dark and financially difficult - to say the least.

　　One such Chinese mother decided to try for another baby at the age of 46 - despite being partially paralysed - so her and her husband's life could have hope again.

　　After undergoing four rounds of IVF treatment in two years and a highly risky pregnancy, Fang Zhiying gave birth to a set of twins at the age of 48 in the Zhongnan Hospital in Wuhan last December.

　　As soon as Ms Fang heard her newborns' first cries, she burst into tears on the operating table.

　　These were the tears of joy for the babies and tears of sorrow for her deceased son, who died as a hero trying to save the others from a massive fire.

　　According to Chinese newspaper Changjiang Daily, Fang Zhiying and her husband Pang Fangguo's only child, Pang Ti, was a firefighter. He was killed aged 24 after being sent to control a series of chemical explosions at a factory warehouse in Tianjin in 2015.

　　The deadly blast is the most horrific chemical disaster China has seen in decades and left a total of 173 people dead - many of them firefighters and the only child such as Pang Ti.

　　The couple, from the city of Suizhou in central China, were completely devastated by their son's death.

　　Ms Fang is paralysed in the right arm and lost the ability to work after surviving a stroke in 2007. She became so depressed after losing her single child that she would sit in her home staring at the ceiling all day.

　　Mr Pang, who was 48 years old when his son died, spent every day looking after his wife. He suggested to her that they should try to have more babies, so that they could have offspring and their life could be lively. Ms Fang agreed.

　　Family is an important concept in the Chinese culture, especially to have your own children and to pass on your family's name. Many traditionally minded people also believe that having children means that someone would look after them when they get old.

　　According to latest statistics, around 670,000 women in China have to live through the bitterness of losing their only child.

　　Some of them managed to have another child when the one-child policy was lifted in 2016, but many were already too old to try for babies again.

　　To bring new hope to their life, Mr Pang and Ms Fang embarked on a challenging journey of becoming parents again.

　　The couple went through three rounds of IVF from April, 2016, but all of them failed. Ms Fang however was determined to carry on so they had a fourth session on May 13, 2017.

　　The couple were ecstatic to find out 14 days later that Ms Fang was impregnated by the last IVF treatment.

　　They had chosen to have twins through IVF because according to them 'the children could help look after each other in the future and visit our son's tomb often'.

　　As a stroke survivor, Ms Fang's pregnancy was extremely difficult. She had to receive injections every day to prevent blood clots; and at nearly 50 years old, it was hard for her to physically carry the twins, so she rarely left the house.

　　On December 14, Mr Pang and Ms Fang's babies were born via a Caesarean section: an elder brother and a younger sister.

　　On February 10, Mr Pang, 50, and Ms Fang, 49, posed for a family portrait holding their two-month-old twins while sitting next to Pang Ti's military uniform.

　　The emotional couple told Changjiang Daily the photo howhad come three years too late and one person short.

　　They have named the twins Si Si and Nian Nian, or 'missing' and 'thinking', to remind them of the eldest brother they would never meet.

　　Mr Pang told Changjiang Daily he and his wife would teach their twins to be the hero Pang Ti was.

　　A long-awaited family portrait:Ms Fang,49,and her husband, 50, hold their twins next to their late son's military uniform

　　Ms Fang, who has survived a stroke and is paralysed in the right arm, sits in her home as she waits for her due date of her twins

　　Mr Pang weeps as he talks about his late son, Pang Ti, who was killed in 2015 while trying to save the others in a massive fire

　　The tears of joy and sorrow: Fang Zhiying, 48, cries on the operating table as she hears her twins were born safely in China

　　Welcome to the world: Mr Pang and Ms Fang's son, Si Si, was born on December 14, bringing hope to the grieving couple

　　Miraculous birth: Their daughter, Nian Nian, arrived two minutes after her elder brother in the Zhongnan Hospital in Wuhan

　　Mr Pang burns an old family portrait with him, his wife and his late son Pang Ti as he visits Ti's tomb after the twins were born

　　The couple is pictured with their twins on March 2 as they celebrate the traditional Lantern Festival at their home in Suizhou