Part of this is sheer numbers: There are more twins today than at any other time in history. According to a report by the National Center for Health Statistics, the rate of twin births rose by 76 percent from 1980 to 2009, when about one in 30 babies born in the U.S. was a twin. Since then the rate has only risen. The products of America’s twin boom are now old enough to be posting to Instagram and YouTube, where they are met with open arms.

“Twins play into something the YouTube algorithm is favoring at the moment,” says Dan Weinstein, the co-founder and president of Studio71, an influencer-management company. “So they’re surfacing more than they used to.” Teenage twin-content enthusiasts told me they liked to dream about what they would do if they had grown up with a twin—a fantasy identical twinfluencers play into happily, tricking their teachers and playing pranks on parents. “Much of twin content plays on this idea of challenges,” Weinstein says, “which frankly have been on YouTube for a long time as a general trend, but it’s very, very easy to play into that subgenre as a twin.”

Twins also have built-in chemistry. “It’s the same reason why couples channels do well,” Alan Stokes, a 22-year-old influencer with 4.3 million followers on Instagram, told me. “Twins are the closest you can get to someone without it being a couple thing.” Alan’s twin, Alex (3.4 million followers), chimed in: “I’ve noticed on YouTube especially, pairs just work better. It makes the video more interesting.”

Having a twin also lowers the barrier to entry to becoming a creator. For influencers to grow online, collaboration is key. Being a twinfluencer means having someone around you to act as a sounding board, brainstorm with, or simply hold the camera. It also means splitting editing and promotion time between two people: While one twin responds to fans via Instagram DM, the other can cut together the day’s YouTube video. This allows each twin to play to their strengths, together acting as one super-influencer. “My sister, Olivia, is more organized than me,” says Ashley Mescia, a 19-year-old influencer. “I’m better when it comes to socializing.”

Meet and greets and brand events, too, are easier with a partner. “Whenever we meet new people, we’re not too shy because we feed off each other. We can fill in the spaces where the other one lacks,” says 18-year-old Myka Montoya, who is one half of the Montoya Twins.

Splitting everything isn’t always painless, however. Some twins said they were more likely to fight with a sibling than a friend. Others mentioned that when you’re a twinfluencer, you can’t have autonomy over your own channel or Instagram account. Maintaining a twin brand, especially as both parties develop their own unique personalities and interests, can be hard. While the Stokes twins maintain a shared YouTube channel, each has an individual Instagram account. “I didn’t want people to only see us as one person,” Alex says. On Instagram, they often match their outfits, though in real life they maintain different looks. But one twin won’t make a change in appearance without the other doing it too.

“A drawback being a twin is there’s two people. You have to share, you have to make sure you’re on the same page all the time, and you have to share attention,” says Jake Randall, a 23-year-old influencer. “People think we get along all the time, but when you live with someone 24/7 for 23 years, it doesn’t always go like that.”