EXCLUSIVE: Khloe Kardashian on Kendall Jenner & Harry Styles' St. Barts PDA: 'To Me, That's Dating'

Khloe opened up to ET about Kendall and Harry's romantic involvement.

Khloe Kardashian says she's pretty sure her sister, Kendall Jenner, is dating Harry Styles.

"Do I think they’re dating? Yes," Khloe told ET's Kevin Frazier, who was first on the set of Kocktails With Khloe on Thursday, where she opened up about the cute couple's relationship status.

"I don't know if they're like boyfriend-girlfriend," Khloe explained to ET. "Nowadays I don't know. People are weird with stuff. So, I don't know their title. But I mean, they were in St. Barts together hanging out, so to me that's dating."

WATCH: Kendall Jenner and Harry Styles Get Cozy in St. Barts -- See the Pics!

Rumors that the two were romantically linked began to swirl over the holidays when they were spotted getting super cozy on a yacht while vacationing together in St. Barts on New Year's Eve.

A source close to Kendall told ET that "there has been something going on with those two for a while" and it was the 20-year-old model "who made the first move," inviting the 21-year-old One Direction member on the trip.

Kendall, who showed off her figure in a string bikini, laid out on the deck of the yacht with a shirtless Harry, who rocked his signature man bun. The two were even caught in what looked like a steamy lip-lock aboard the ship.

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"I would call that dating," Khloe said. "[But] I don't know what they are. You know, you have the have 'the talk' [and] I don't know if they've had that talk yet."

"Kendall doesn’t want to get hurt, so she’s proceeding with caution," the source maintained. "She knows what the deal is."

After their steamy alone time, Kendall and Harry spent New Year's Day hanging out with Ellen DeGeneres and her wife, Portia De Rossi, for lunch on a C2 mega yacht.

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At the People's Choice Awards on Wednesday, Ellen may have inadvertently confirmed the duo's couple status when she spoke with ET backstage after the show.

In gushing over Harry and Kendall, the talk show host insinuated that the two are romantically involved, saying, "They're very sweet. "I like both of them individually and I like them together as well."

WATCH: Did Ellen DeGeneres Accidentally Out Harry Styles & Kendall Jenner as a Couple?

Kocktails With Khloe premieres Jan. 20 on FYI.

Tune in to Entertainment Tonight on Friday for more from our on-set interview with Khloe. Check here for local listings.

For more on Ellen's inadvertent confirmation of Kendall and Harry's relationship, check out the video below.