Davis Gestiehr, 12, sings the national anthem at the Verizon Center before the beginning of a Washington Wizards basketball game. (Astrid Riecken/ The Washington Post)

My boys fight about toys. They fight about the dog, the cat, dinner, lunch, breakfast, the television, the car, the sun, the air.

So lately, I’ve been asking people about their sibling relationships and how they avoid felony charges when it comes to them. Some don’t, as evidenced by the 14-year-old kid in Idaho who shot his father, then shot, knifed and hacked his younger brother with a machete. Scary.

But some siblings are soul mates rather than rivals. Remember the twin biathlete sisters this winter? One qualified for the 2014 Olympics and the other didn’t, but the qualifier gave her spot on the Olympic team to her sis? How do I get some of that?

Then I met the Davison Duo, musician kids who live in Bethesda. Madison and Davis Gestiehr are sister and brother. She is 15, and he is 13.

Oh, they insist they fight.

“We fight about the charger. The phone charger. And who gets to use it,” said Madison, on the way to one of the voice lessons she and her brother take every week.

“Or we’ll grab a phone from each other to see an Instagram,” Davis said.

That’s all? “Yeah,” they nodded their heads. “These days.”

Because these days, they have more in common than most brother-sister pairs. In between Spanish and chemistry and taekwondo and two soccer teams, they are entertainers.

“Sometimes we’ll come home from a bar late at night,” said Davis, who looks much younger than 13 behind his ginormous acoustic guitar and behind the muscular, roof-raising notes he hits you with.

“If your kid is really into soccer or baseball, you take them to professional games. But when your kids are into music, you end up in bars,” said Chip Gestiehr, their dad. “They’ve met lots of drunks.”

Mom Debby Davis Gestiehr sometimes gets an earful from other parents who don’t think the bar-dwelling is appropriate. “My hope is, by the time they’re old enough to drink, they will have seen enough drunks act dumb to not want to do it themselves.”

They go out to hear a lot of cool music. And then they play punk and rock and coffeehouse music in gigs all over town.

Davis makes a great frontman. The audience sees his skinny jeans, his Chucks and a smile straight out of Cracked magazine. And then — smack! — he belts out this big, emotional wall of sound about love and loss. And Madison builds a strong foundation with her rich vocals and aggressive, nimble guitar playing.

“Sometimes, we need to figure out how to sing these songs and what they mean,” she said.

Yeah. It might seem weird to hear tweens from Bethesda roar about blood running stale, cards folded and dark demon beasts inside. But their voice coach, opera singer Lisa Carrier Baker, analyzes each of the songs so they can relate to them.

“Like the Imagine Dragons song ‘Demons’?” Madison said. “For me, the demons are, like, homework.”

And wow, that homework must hurt, because when she sings, you can hear pain and shimmering love and deep darkness.

They say it’s not hard to get up in front of people and sing. Unless their friends are in the crowd. That’s always tough.“I like playing in front of strangers because you don’t know the adults, and you can always see the surprise on their faces,” Davis said.

He did his first gig when he was in kindergarten. And both kids say they want to be musicians when they grow up. So their parents must be pretty strict about practice, right?

“We practice every day, for about an hour,” Davis said.

Do their parents hound them to get to it? “No. It’s a release. It’s a break from the stress, from the homework. I love it when we get to play,” Madison said.

Here’s the part of the story that I really love.

Davis has A Voice. When he was a tyke, his gorgeous notes on anything from “Wheels on the Bus” to “Row, Row, Row Your Boat” soared above all the other voices and made everyone stop.

And that still happens today. He sings an eloquent and chilling national anthem. You may have heard him at a Wizards game or an Orioles game. He’s opening a Nationals game next week. Madison, who studies sign language, sometimes signs along with Davis when he performs the national anthem. She picked up music after it was clear that Davis was going to blaze ahead with That Voice and she’s become their songwriter. But aside from the anthem gigs, Davis refuses to leave his sister behind.

Two years ago, one of the big, national talent shows asked Davis to come and audition. Without his sister.

“Nope,” he said.

“She keeps me grounded,” Davis said. She’s his other half, he said, and he won’t go on without her. The show’s producers asked again last year. This is a pretty big deal. These are the kinds of shows that people wait in line for hours to audition for. But one of their talent scouts heard Davis and has been pursuing him ever since. Nope again. Not without his sister.

They asked again this year. And finally, he went. With Madison onstage beside him. I can’t tell you more than that because they had to sign all sorts of confidentiality agreements until the show airs.

But I immediately thought about the rivalry between my sons. Music lessons, boys?

8 To read previous columns, go to washingtonpost.com/dvorak.