When Wan Li's first daughter Duo Duo was born six years ago, the oil painter was unprepared to be a father. But his two daughters are now his inspiration and he now sees himself as "a painter for daughters".

Wan's Daughter series of paintings is now on display in Nanjing, Jiangsu province.

On his canvases, his daughters are dressed in traditional Chinese costumes, catching butterflies, sitting under a tree or playing along a river.

Theses portraits went viral online and have attracted tens of thousands of likes.

The artist has done oil painting for years. But he also does traditional ink painting.

In his works, Chinese ink painting elements are combined into his oil works.

"It's not easy to mix oil painting with traditional Chinese ink painting," says Wan, 32.

When his older daughter was 2 years old, Wan painted the first portraits of her and kept doing this to record her childhood.

His daughters' clothes and accessories for the paintings are chosen by his wife Feng Yan, an interior designer. His daughters - aged 6 and 3 - also like to wear these clothes in daily life, he says.

The older girl enjoys being in Wan's studio in Nanjing and is learning calligraphy from her father. And the younger one typically follows her sister.

At Wan's studio, hundreds of pictures recording his daughters' lives hang on a big board. And he has a special space in his studio to take photos of his daughters.

"It's very hard to keep them quiet and still. Mostly, they just play with toys, and I watch them playing," says Wan.

When Duo Duo was 4 years old, Wan gave her a flower toy and took a photo when the little girl crawled to get it.

Then, on his canvas, he changed the toy into butterflies, inspired by an ancient Chinese ink painting focusing on butterflies.

So far, Wan has painted 14 portraits of his older daughter, which makes the younger one jealous.

As a result, he has just done the first one for the 2-year-old, depicting her standing in a river with lotus flowers around.

"Meng Meng is naughty. She posed for just two photos and ran away," says Wan, explaining why he only produced one portrait of her.

Wan says the painting experience makes him feel that his daughters are growing too quickly.

He says he still remembers her older daughter's chubby face when she was 3.

"I want time to slow down and enjoy the lovely moments. Sometimes, I imagine what they will look like in the future. The works make me really happy," he says.

A painting typically takes him one or two months to complete. And he enjoys the painting process.

"I will keep painting them. When they grow up and see these pictures, it's a love legacy from their father."

Wan learned oil painting from Zhuang Tianming for more than two decades.

Zhuang promotes the combination of Chinese ink techniques and oil painting skills.

He encouraged Wan to produce a series of portraits of his daughters by mixing Eastern and Western styles.

"His oil paintings of his daughters let viewers know at the first sight that it is a Chinese oil painter at work," adds Zhuang.