Kicking a ball back and forth in a small passageway in their three-bedroom flat in Yau Tong, Shing-shing, three years old, and Billy, five years old, are clearly having fun. Although the space of just over 700 sq ft is a squeeze for three single-parent families, it's a step up from the subdivided flats in which they used to live.
The two boys are in good spirits, as are their mothers, both gradually rebuilding their lives after heartbreaking personal setbacks.
"We used to live in a subdivided public housing flat with five other people," says Billy's mother, K.K. So.
The 30-year-old moved here from Qingyuan in Guangdong when she married a Hong Kong man and it wasn't long before Shing-shing was born. But the family unit didn't last.
"In 2011, I got my Hong Kong ID card and then one day my husband left for the day and never came back," So says. "I called his mobile many times, but there was no answer and eventually the phone was disconnected. I filed a police report, but I have not heard from him since."
So's relatives in Hong Kong could only offer limited help, which is how she and Billy ended up living in a tiny room in a subdivided flat, just big enough for a bed and their few belongings.
"I would take my son to kindergarten and then go home right away because going out means spending money, which - being on welfare - I didn't have," she says.
Their tiny living space became their entire world: it was where she would stay until it was time to pick up Shing-shing, and where she cooked and served dinner before they went to bed.
Her luck changed last year when she met Ricky Yu Wai-yip, founder and CEO of social enterprise Light Be, which recruits property owners who are willing to rent out flats cheaply to groups of single-parent families.
Yu introduced her to two other single mums and proposed that the three families share a flat.
"My son is much happier. He is more sociable and has a table to do homework," So says.
Shing-shing isn't the only one who has benefited from the new living conditions.
"At first So was very shy and not confident, and felt she had no skills," Yu says. "But gradually she has come out of her shell, started volunteering and now she's really interested in becoming a social worker."
So says: "I'm learning how to help people and attending classes. I want to help other people who are in the same predicament as me. I've been through it so I know how hard it is to find people to help you."
So's newfound self-belief is one of many positive outcomes Yu has achieved since he founded Light Be.
Yu feels for his charges, having grown up in public housing, after his parents settled in Sham Shui Po when they migrated from the mainland following the second world war.
"Housing is so important because it's a big part in relieving poverty," he says.
"In the 1970s and '80s, we were all the same [in terms of income levels]. We didn't need security features, like locks or guards. When there was a thief, everyone helped to catch him, and we shared our food. When you have good neighbours it affects a person's development."
Yu was working as general manager at direct selling firm Amway Hong Kong when he became concerned about the plight of people living in subdivided flats.
What bothered him was not just the dire conditions, but also the isolation that comes from being closed off in tiny rooms without knowing who lives nearby.
"It creates a sense of insecurity and makes it hard for people to stand up for themselves. Because of that they have no motivation to try to improve their situation as they are constantly in survival mode.
"They are thinking of things like: 'Will the landlord kick me out? Will the toilet overflow?'
"They need support to get them out of the cycle and a home is a foundation. That with other poverty relief will make a big impact," says Yu.
In 2010, he quit his job to set up Light Be, and secured some incubation money from Francis Ngai Wah-sing, founder of Social Ventures Hong Kong.
By last September he was able to rent out the first unit to three families, who he found through social welfare groups SoCO and New Arrival Women League.
Light Be has since expanded to provide leased flats in seven districts, including Central and Tuen Mun.
The first of the properties came from RS Group, the philanthropic investment vehicle of Annie Chen Ang-yee, a former lawyer who has been directing her inheritance towards ventures that achieve positive social or environmental impacts and financial returns.
"This project explains impact investing in an easily understandable way for Hong Kong people because it's about property. Real estate is so much a part of the Hong Kong fabric and it's a topic everyone cares, worries and thinks about," says Chen. "A physical home plays an important part in everyone's life. It's a big issue in Hong Kong because having a home helps people take the next step in their lives."
The experiment has proved effective enough that RS Group has since contributed two other flats to the Light Be scheme.
Sharing a home with several families takes some getting used to, but So's flatmate S.K. Lo is glad that she no longer has to climb several flights of stairs every day with groceries in one hand and her son hanging from her side, as she did when she rented space in a subdivided tong lau in Kowloon.
"The environment here is better, and it's good for my son. He's in kindergarten but I can't help him with his English homework because I don't know the language," she says.
Like So, she came to Hong Kong to marry. But when her son turned two years old, just over a year ago, her husband, a manual worker, died suddenly after developing a flu-like illness.
Lo was not only grief-stricken, she had no way to raise her son on her own. She had few skills and had yet to qualify for an ID card, which made access to government help difficult.
"I didn't know what to do," Lo says, her eyes welling at the memory of her husband's sudden death.
Friends from a church group eventually put her in touch with Yu, who helped her settle in the Light Be flat. Lo is trying to secure a part-time job that could fit around her son's school hours. However, she isn't giving up; she hopes to pick up English and gain computer skills so she can eventually make a better life for herself and her son.
Yu has been delighted with Light Be's progress in the past year. He calculates his tenants' rent according to their income or welfare subsidies, and takes a slim cut to fund the project.
So far it's working: none of f the tenants have been late with their payments, and the grateful women are plying him with home-made soup whenever he visits to collect the rent.
"We have quashed two assumptions in Hong Kong: one, that there are no places for low-income families to live and, two, that all landlords are cold people," says Yu.
"Every month we get calls from landlords inquiring about the programme. This shows not everyone is materialistic and it makes me very optimistic about Hong Kong's future."