Kaia Gerber's brother got her name tattooed on his body — is that weird or what?

Presley Gerber is showing off his new tattoo, a tribute to his sister Kaia, a gesture social media is calling both “cute” and “weird.”

Eighteen-year-old Presley inked the 16-year-old model’s name on his left arm along with the Roman Numeral 23, at Bang Bang Tattoos in New York City, with girlfriend Charlotte D’Alessio and Kaia present. On Thursday, he revealed his art on Instagram to a medley of mixed reviews: “Best bro forever!” “Yaa even I find it kinda creepy,” and “A tattoo of your sister’s name? That’s just weird.”

It’s a mystery why Presley chose the number 23, but some guessed it’s in honor of Kaia’s January 23rd couture show debut at Chanel during Paris Fashion Week.

The Gerbers weren’t the only brother-sister duo to stir comments this week about their closeness. U.S. Olympic figure skaters Maia and Alex Shibutani’s bronze-winning performance was overshadowed by commentary that their routine was too close for comfort.

This week, Alex addressed his critics in an Instagram post. “Throughout our career (14 years and counting), we have had to, and will continue to push past stereotypes, labels, doubters, and cynics,” he wrote. “We have become successful BECAUSE we are siblings and family. Not in spite of that fact. We have challenged ourselves to grow, innovate, and embrace what makes us different from other teams BECAUSE our differences are what make us unique.”

Research shows that two-thirds of siblings have a tight bond, calling their other half as their “best friend.” That closeness could stem from a shared history, an intimate understanding of each other as people, or comfort in their unconditional connection.

But is it possible for siblings to be too close? “Each family has their own culture and shorthand and it’s important for kids to also have friends outside of that circle so they learn to form new types of connections,” Deborah Gilboa, M.D., parenting and youth development expert, tells Yahoo Lifestyle.

Healthy sibling relationships are the result of an equal social power dynamic, explains Gilboa. That means one isn’t given more attention than the other from their parents and siblings treat each other with respect.

Who knows if that exists between the Gerbers and Shibutanis but a sibling tattoo, for example, is not an indicator. “The tattoo could be an inside joke, the result of a dare, or an expression of love,” says Gilboa. “Frankly, if an 18-year-old is getting a tattoo, it’s probably better to have the name of a permanent sibling than a fleeting romantic partner.”

As for the Shibutanis, there are two potential reasons the public is taken aback. “Ice skating is considered an expression of romance — partners gaze into each other’s eyes and there’s a lot of touching — so people may be focusing too much on that,” says Gilboa.

And since an Olympian isn’t an every-day job, there’s little understanding or context for the type of discipline and healthy boundaries required when siblings pair up. “Most people can’t picture training for the Olympics but they can picture spending months on end with a sibling,” says Gilboa. “So, if they say, ‘I would kill my brother if we spent so much time together’ they’re speaking with their own biases.”

There are lots of ways siblings express their bond — they become roommates, business partners, some even have double weddings — and that’s typically a result of a healthy upbringing. “It’s difficult to create a culture in which siblings have lifelong respect for each other,” says Gilboa. “Kudos to their parents.”

Read more from Yahoo Lifestyle:

• Should Melania Trump forgive her husband for his alleged affair? Americans have lots of opinions

• Is love at first sight real? Meghan Trainor thinks so — but what about relationship experts?

• Lisa Bloom, who is Gloria Allred’s daughter, just hired her daughter at her law firm. Is that taboo?

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