A 7-year-old girl in rural China says she's not sure her mom can tell her apart from her twin sister. It's been too long since their mother, a migrant worker, has come back home.

It's a scene in a new 4-minute documentary from Coke that draws attention to the millions of Chinese children whose parents have left them behind as they seek jobs in cities and factory towns. Ahead of Chinese New Year, Coca-Cola reunited three families, building on its brand message about connecting people.

McCann Shanghai produced the video being shared on social media and shown on taxi screens before the holiday starts Friday. It's prompting viewers to share their own regrets about being far from home for the holidays and generating social media discussion about China's "left-behind children."

About 61 million kids live separately from one or both parents, the All-China Women's Federation says. Children often stay with relatives in the countryside while their parents work far away, sending money home and coming back to visit for the lunar new year.

It's a huge travel time: Chinese authorities expect people to make 3.6 billion trips this year.

Coca-Cola filmed a similar documentary in the Philippines for Christmas 2011. In China this year, it brought parents back to their hometowns a few weeks early for the holiday. Shooting wrapped in early January.

In a country where brands often turn to celebrities, documentary footage about children in rural areas stands out.

"We wanted to touch on something real, not manufactured, and we found a great cast and had some great discussions when we were casting for them," said Richard Cotton, Coca-Cola's director of content and creative excellence in China.

A separate Coca-Cola TV commercial in China also touches on connection, urging people to put their cell phones down for the holiday and pay attention to family and friends.

The lunar new year is when brands often bring out their most heartfelt or ambitious work in China. For several years Pepsico has run a successful multibrand campaign called "Bring Happiness Home," which has involved mini-movies, theme songs and charity efforts.