Para-swimmer Yip Pin Xiu's parents were 15 minutes late for the interview.

Apologising, Margaret Chong said she and her husband, Yip Chee Khiong, had been picking out Havaianas flip-flops from a shopping mall in Rio.

They were bringing home the popular Brazilian footwear brand for family members, though not for their only daughter, 24-year-old Pin Xiu.

The couple both 61, were in Rio where they watched her compete in last Thursday's (Friday morning, Singapore time) 50m backstroke S2 event, where she became the first Singaporean to win multiple gold medals at the same Games.

Dad, a businessman, recalled how it was Pin Xiu's inability to keep a pair of flip-flops on her feet that was the first hint something was amiss. At two, the toddler was unable to grip the straps with her toes or flex her foot fully.

Pin Xiu was taken to a doctor, and had surgery to release what were thought to be tight tendons, but the doctor noticed that her muscles did not seem to be growing even after the cast had been removed.

Medical tests confirmed she had muscular dystrophy, a genetic muscle-wasting illness, and that there was no cure.

Tears still well up in Mum's eyes now as she recalls how upset she was when they were told the news.

"I was worried about her future and about things such as whether people would want to make friends with her," she said.

"The doctor advised us to let her be active to remain mobile for as long as possible."

Looking back now, their fears were unfounded, said Margaret, a senior officer with Singapore Airlines.

Pin Xiu has a group of close friends who are athletes and she is as independent as any able-bodied person, even as her condition continues to deteriorate.

Perhaps the water called to her as a kinder place than land. In any case, at age five, she asked for lessons after watching her two older brothers learn their strokes in the pool. Alvin, 31, now works in finance and Augustus, 29, is an engineer.

Alvin said his sister is "extremely thoughtful", recalling how she made time to accompany his pregnant wife to hospital daily in June when he was overseas.

"We knew she was tired from her training twice a day, but she still went anyway, which helped put my wife at ease," he said.

"I rushed from the airport to visit my wife and newborn and saw that Pin Xiu was still there even though she had morning training in a few hours' time."

Sunday mornings became about family time at the pool at the Kallang Bahru Swimming Complex. It was here that the future champion first tasted failure - she could not complete a swim test, at half the distance done by others, in the stipulated time. Disappointed, she wept.

But still, she pressed on. When the complex was closed for renovation, she continued lessons at Jalan Besar, where a sports volunteer spotted her talent. A few months later, she was entered in the national junior para championships, where she won gold in all of her six events.

By then, Pin Xiu was swimming two hours every night on weekdays. Dad would drive her there and back, and she would have dinner in the car.

But as Pin Xiu became faster in the pool, she grew weaker on land.

At four, she needed an ankle-foot orthotic brace to assist her with walking. By 12, she had to hold on to the wall or a friend's shoulder to steady herself while walking with the brace.

By the time she enrolled in Bendemeer Secondary School, she was in a wheelchair.

The family is grateful that she was well taken care of in school, with teachers giving her access to a staff toilet that was bigger and could accommodate her wheelchair.

The reigning Straits Times' Athlete of the Year has said in past interviews that she was bullied in school, but her mother could only remember the kindness of classmates who helped carry her and her wheelchair up the stairs to class.

The Yips never thought as far ahead as the Paralympics. But they knew she had something special.

When Pin Xiu won the 100m backstroke S2 on Sept 9, she set two world records in the process.

She had also won the nation's first Paralympic gold in 2008 in Beijing in the 50m back S3, as well as a silver in the 50m freestyle S3.

Four years later, she finished fourth in both events in London.

Yet, even as their daughter grew from strength to strength in the pool, the Yips had their own Olympic-sized quest.

Margaret said their greatest challenge was the ceaseless quest to find someone who could cure her or help her live as full a life as possible.

For Pin Xiu, trips to clinics and hospitals were almost as routine as time in the pool. The Yips sought help from mainstream treatment to traditional cures and Pin Xiu obediently downed bitter concoctions and allowed herself to have almost-daily leg massages.

She took it all in her stride.

"She will just do whatever you say can help her legs," said Mum.

It was Pin Xiu's medical bills, and not her swim training and competition expenses - most of which are paid for by the Singapore Disability Sports Council - which have been the greatest burden on their finances, one they bear willingly.

Mindful of their daughter's happiness, the Yips were never stressed about how training could affect Pin Xiu's studies. Swimming took precedence over school in 2008, the year she sat her O levels.

Margaret said: "I told her if she didn't do well, she could just repeat the exam."

She did well enough to become a sports and health student at Republic Polytechnic.

This year, she deferred her final-year studies at the Singapore Management University to concentrate on preparing for the Rio Games. Mum said she would have graduated in July otherwise.

By giving their talented and single-minded child the space to think and make choices for herself, Pin Xiu's parents have encouraged her independence. In fact, the soft-spoken pair are hard-pressed to think of instances when she needs help around the house.

Margaret finally thinks of something: Sometimes Pin Xiu needs items in her wardrobe she cannot reach. "She may tell me in advance what clothes she'll like to wear the next day and where these are exactly, so I can get them for her."

She also needs help getting into her tricky competition swimsuits, which her close friend and fellow swimmer, Theresa Goh, lends a hand with. Her waist-length hair is tucked into her swim cap by coach Mick Massey, who also holds her hands before the start of a race because she cannot hold the bar on her own.

But she gets around on her own by cab, is an expert at texting with her thumb and knuckles, and opens bottle caps using her palms.

A few months ago, she cooked her own meal and proudly sent pictures to her parents and brothers.

And she has done what most people never would, in reaching the pinnacle of her chosen sport.

Her parents, who were present at the Olympic Aquatics Stadium for Pin Xiu's second final, say they could not have wished for more.

Said Mum: "Seeing my children so independent, I always tell them that I can close my eyes now and go."