They were born thousands of kilometres apart but grew up together, skated together, and went to school together. When they take to the ice at the Pyeongchang Winter Olympics, though, the Brandt sisters will once again represent different countries.
Marissa was given up for adoption soon after her birth in South Korea, one of hundreds of thousands of children who found new families overseas as the country -- once known as the world's top baby exporter -- underwent rapid industrialisation.
Months later Robin gave birth to her sister Hannah.
Typically for their state, the girls grew up skating regularly, and now both have won national ice hockey team places.
But while forward Hannah will play for the US at next month's Games, Seoul restored Marissa's South Korean citizenship as it sought recruits to bolster its side, and she will represent the country of her birth.
It is a family story that blends issues of identity, ethnicity and adoption against a backdrop of sporting rivalry.
As a young Asian girl growing up in an American family, Marissa sought to ignore the colour of her skin, and sought to emulate blonde, pale Hannah.
"I just wanted to fit in and not look different from my sister," Marissa told AFP.
Sport was one of the ways she did so, switching from figure skating to ice hockey to follow in Hannah's blade tracks.
"We were always best friends and did everything together," said Hannah, 24.
They played on the same teams -- Marissa is a defender -- until they went to different colleges.
And their trajectories moved even further apart when the Korea Ice Hockey Association started scouring through colleges across North America, looking for ethnic Korean players as it scrambled to create a team good enough to avoid humiliation when it hosts the Olympics.
South Korea has only 319 registered female hockey players of its own, according to an International Ice Hockey Federation survey last year.
Marissa was identified as a likely prospect, and invited to try out for the side in 2015.
It was the first time she had returned to her birth country since her adoption, after years of distancing herself from its culture and language.
"I was excited and curious but also nervous and didn't know what to expect," she said.
Sailing into the squad, she received a South Korean passport the following year, and her jersey is emblazoned "Park Yoon-Jung", the name on her US adoption papers.
"I chose to wear my Korean name on the back of my jersey because that was really my only tie to Korea," she said.
The past three years have been a journey of reconnection, and now Marissa loves to go out for Korean style beef barbecue bulgogi and meat dumplings, and cranking up K-pop music with her teammates in the locker room.
Now, she says, "I consider myself Korean-American. Whereas before I would only consider myself American.
"I can finally say that I am proud to be Korean."
The South Korean team -- who qualified as hosts, rather than on merit -- includes three other foreign recruits, and has now had 12 North Korean players added to create a unified Korean team as diplomatic relations on the peninsula enjoy an Olympics-driven warming.
The Brandt sisters are unlikely to play each other, with the powerhouse US team in a different pool and Korea unlikely to go through to the semi-finals.
Even so the prospect is a topic of family humour. "We always joke about who our parents would cheer for if we played against each other!" said Marissa, who describes adoption as "a great thing".
"I think adoption is important for children to find great homes and feel loved," she said. "I'm very thankful my birth mother gave me up for adoption. She wanted me to have a better life which I appreciate."
But she has one further goal off the ice while in the South: she would "obviously love" to meet her.
With little information available, though, Marissa knows it is her longest shot of all.
"I don't know her name," she said. "I just know she had olive skin and a round face. So I have basically nothing to go off of with trying to find her."
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