Twins from China who were separated at birth and adopted by two different families in the US have been reunited for the first time.

Identical 10-year-olds Audrey Doering and Gracie Rainsberry embraced each other and cried as they met for the first time on ABC's Good Morning America.

They grew up hundreds of miles away from each other after being adopted shortly after birth by two different families - Audrey in Wausau, Wisconsin, and Gracie in Richland, Washington.

Neither of their families knew that the girls had a sibling until December when Audrey's mother found a photo of both of them together as babies, posing with their Chinese foster mum.

Jennifer Doering became curious about her daughter's past while she was trying to find a Christmas present for her. She wanted to give her daughter a copy of her "finding ad" - a photo that gets published in Chinese newspapers when a baby is placed in an orphanage.

With the help of a Chinese researcher, she discovered a photo that showed her daughter on the knee of her Chinese foster mother, who was carrying another baby that looked just like Audrey.

"As soon as I had that picture, I was desperate to find out... who that other child was," Doering said, according to an ABC News report.

Doering eventually found out that the other child was her daughter's twin, who had also been adopted and taken to the US.

"Oh, it was unbelievable. I'm like, 'How?' I mean, this is stuff you read about," Doering said. "And how, how could it really be that there are two of them?"

With the help of Facebook, Doering was able to find Nicole Rainsberry, Gracie's mother, said ABC News.

Gracie's mum Nicole Rainsberry said that finding out about her daughter's twin was "surreal."

"I mean, it's hard to process that information," Rainsberry added. "It was so crazy to be looking at what looked like Gracie, but knowing that it wasn't Gracie."

The families also discovered that the twins both suffered from heart conditions. Gracie underwent two heart surgeries after arriving in the United States and Audrey underwent one, their families told GMA.

The twins have also found out that they share a love of the same foods - chicken Alfredo, and macaroni and cheese.

Audrey said when she heard the news that she had a twin, "I thought my parents were, like, playing a joke on me."

She added that when she video chatted with her sister for the first time, her initial reaction was that "she's me".

Gracie Rainsberry said that when first found out she had a twin she was "really overwhelmed," reported ABC.

"I... started to cry a lot, and my mom kept on asking me... what my crying was for, and I was saying, 'I don't know'," Gracie said. "I didn't know what to think."

Shortly after their live TV meeting, Gracie said she was feeling excited and happy.

"It's very overwhelming," she said.

Audrey said, "it felt like there was somebody missing".

"Now, it's complete."