They have squabbled on the ice since they were kids. Now they're a united force, making Olympic history and going for the gold in Pyeongchang.
Siblings Matt and Becca Hamilton of McFarland, Wis., are the first brother-and-sister team in the new competition of mixed doubles curling, that strange-looking sport that fascinates anew every four years.
"Four years ago they announced that it would be an Olympic sport," Matt, 28, told InsideEdition.com. That's "when we decided that we should try out for it because it is another opportunity in the Olympics and (the) brother-sister duo. Who could beat that?"
The Hamiltons have also qualified for single-gender curling, meaning they could be on the ice for up to 50 hours over 18 straight days. Curling is the longest of any Winter Olympic sport, starting before opening ceremonies and ending hours before the Olympic torch is extinguished.
The 600-year-old sport of pushing a 44-pound "stone" across the ice with a "broom" looks like a weird hybrid of bowling and house cleaning.
Matt calls it a mix of shuffleboard, chess, and bowling. "Oh, and Swiffering your floor," he said.
Becca's big brother got into curling before she did. But his initial impression of it was lackluster.
"My dad went down to the club and played in leagues and when I went down to watch him," he said. "I thought it was lame, to be honest."
But as a freshman in high school, after a friend's uncle asked him to come out on the ice, "I just loved it. It was awesome."
About two years later, during a practice session, his coach grabbed Becca, who was watching her brother play.
He said, "You're going to go out and play. You're going to try."
So Becca "reluctantly, kicking and screaming, got into it and found out that she had a love for it, too, and then we just went with it [and] tried to see where it would take us," Matt said.
He's been curling for 16 years, with Becca on the ice for about 14 years.
"He brought me into the game, so I guess what better partner can I find than someone that brought me up?" said Becca.
"She couldn't find a better partner," said Matt.
"I probably could," his sister shot back.
They've been good naturedly bickering like this for most of their lives. But on the ice, they don't even have to talk to each other to know what move to make next. And they talk straight with each other, with no hard feelings.
He is the exuberant one. She is the calm presence that pulls him back into the game.
But she's more than excited to be in South Korea.
"Just to go to the Olympics, and be there when other sports are competing and be part of that community with USA on our back, it's just going to be a dream come true," she said.
The most excited of all, however, is their mother.
"Oh, mom's mind has been rattled," said Matt. "Mom's world has been shaken in the last two months. It's just... she can't believe it. She really can't.
"She's just running around telling everyone under the sun that she is the mother of two Olympians. She loves telling people about it."