As the weather warms, Liu Xing is welcoming more and more customers to her grilled oyster stall at a night market in Harbin, the capital of Heilongjiang province.

"During the past two months, I have been able to earn about 300 yuan ($46) a day," said the 28-year-old.

But the money that flows in is only a fraction of what she needs for the treatment of her 4-year-old triplets.

Liu's daughters, who were born in 2012 in Bei'an, a county 340 kms from Harbin, initially brought great happiness to the family. But the happiness turned to worry when the girls were diagnosed with cerebral palsy when they were 17 months old.

Doctors said at the time they would not be able to walk because of the disorder, which affects a person's ability to move and maintain balance and posture. Liu was comforted by the doctors' assertion that the girls were expected to have normal intelligence and language ability.

"The doctors told us that, after treatment, it would be highly possible that the girls would be able to recover the ability to walk normally. But the treatment would cost at least 600,000 yuan, which was an astronomical number for us," the young mother said.

But the family didn't give up. Although they had moved to Yantai in Shandong province after the triplet's birth, they decided to move to Harbin in order to see doctors at better hospitals.

The couple set about scraping together the money they needed for the triplets' treatment by doing odd jobs at first and then by opening their grilled oyster stall in May 2015.

Liu said more people began to know the family's story after it was reported in local media, and since then, many people have tried to help. She said they were offered the stall at the busy market without needing to pay any administrative fees. And the boss of the seafood market where they buy their oysters offered them a much lower price.

But what touches the couple the most is the kindness of strangers who drop by their stall with money or who send cash without leaving their names.

"Some people have told me that they have come to the stall from far away especially to buy our oysters, and some people have left money without even taking any oysters away," Liu said.

"So far, we have received nearly 300,000 yuan in donations."

Last year, the couple took the triplets to Shenyang, the capital of Liaoning province, where they received two rounds of treatment at a local hospital. "Every round of treatment costs about 180,000 yuan, and the daily rehabilitation services cost about 9,000 yuan a month," Liu told China Daily.

But she said the treatment has led to a great improvement and the triplets can now walk slowly with the help of orthopedic shoes.

Even though the couple has a heavy burden to shoulder, the smiles never vanish from their faces.

"We don't know how many difficulties we will have to face in the future, but we will never give up," Liu said.