Joe Jonas Wore A Justin Bieber T-Shirt At The U.S. Open, But It's Not Just Because He's A True Belieber — PHOTO

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The Jonas Brothers can't stop challenging people to t-shirt duels. On Friday, Joe Jonas wore a Justin Bieber T-shirt during a match at the 2019 US Open, and the garment had an interesting twist. At first glance, it may look like Joe Jonas' attire is regular Belieber merch — but there's another layer to the JoBro's shirt choice. In the photo printed on Joe's shirt, Bieber is actually wearing a throwback Jonas Brothers shirt, creating a fun game of shirt inception.

Nick Jonas was also on hand to support his brother's bold fashion choice (OK, and also to watch some tennis). Both stars were photographed attending the high-profile tennis competition at the Billie Jean King National Tennis Center in Manhattan. Nick and Joe were taking a day off from the Jonas Brothers' Happiness Begins tour, which will continue with dates across the United States throughout September, according to the band's website. It seems the two stars wanted to use the outing to have a bit of fun, though it's not yet clear if Bieber will respond to Joe wearing his likeness on the shirt.

For Joe, this may be the beginning of a shirt-inception showdown, to which Nick is now a veteran. Back in 2018, Stamos wore a vintage Jonas Brothers t-shirt on the red carpet during the American Music Awards, revealing himself to be a major JoBro fan. Stamos' fashion statement didn't go unnoticed — in March, Nick Jonas wore a hoodie printed with a picture of Stamos wearing the 2009 Jonas Brothers' tour shirt, and posted a photo of the garment on Instagram. Nick wrote in the caption: "It’s your move @johnstmos @jonasbrothers #sucker."

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Stamos accepted the challenge. On March 6, Stamos tweeted a picture of a pillowcase printed with Nick Jonas' Instagram photo, captioning it, "Had the craziest dream last night...#jonasbrothers #sucker." The Jonas Brothers' loved his response, and retweeted the photo, writing, "Bravo" with three clapping hands emojis.

Fans may have seen the latest shirt-challenge coming, as it was no secret Bieber owned a throwback-Jonas Brother's shirt as well. In July, Nick posted a photo of Bieber on Instagram. In the photo, the "Sorry" singer can be seen sporting a t-shirt with an old Jonas Brothers band photo on it, embarrassing hairstyles and all. The Jonas Brothers were a good sport about the photo — Nick captioned the picture on Instagram, "He gets it" with a sunglasses emoji.

In the comments, Stamos seemed concerned Bieber was coming for his Jonas Brothers shirt glory. He commented, "Wait! — whoa, whoa — hold on there cowboy!"

It's unclear how and if Bieber will respond to Joe's shirt-ception. There are a few options — He could wear a t-shirt with a picture of Joe Jonas' wearing a t-shirt printed with a picture of Bieber wearing a Joe Jonas' t-shirt, but that might just get a little too meta. For now, fans will just have to wait to find out if Bieber is a sucker for a t-shirt competition, or not.