A source tells PEOPLE that Kendall Jenner, 17, has made a love connection with rapper Young Jinsu, 21.
"They're dating – it's been at least a few months," says a source close to the couple. "They've been getting closer recently, and they've been hanging out all the time."
The source says the couple have kept their relationship quiet but plan to go more public after her 18th birthday on Nov. 3. "They have that spark right now – they're just really feeling each other," says the source. "They're not putting it out there yet."
The rapper recently posted a photo on Instagram of what appears to be him and Jenner, who is making a heart shape in the sky with her hands. Kendall's sister Kylie, 16 – who has been seen in the company of Jayden Smith and rapper L'il Twist, a friend of Jinsu's – posted the pic to Instagram as well.
Jinsu was previously linked to Justin Bieber's ex, Jasmine Villegas. Back in June, he feuded with the superstar on Twitter. But now, he only has eyes for Kendall, whom the source says he started dating – and "falling hard for" – this past summer.
"He's so sweet," says the source. "He kind of reminds you of Chris Brown, but way more charming and really talented. He's been working with a lot of big-time producers and artists recently."
Meantime, Kendall's fast-lane lifestyle with Kylie has raised a few eyebrows. On Oct. 15, the pair were spied in the wee hours at racy L.A. Nightclub Vignette with big sister Khloé Kardashian and Scott Disick.
"They were all inside at the back right table, dancing and having a really good time," an onlooker said of the clan, who attended the Day By Day Fashion Show in downtown L.A. earlier in the night.
Family sources say parental disagreement over how Kylie and Kendall were being raised was a factor in Bruce and Kris Jenner's separation. Bruce is said to disapprove of them being taken out of school for modeling and public appearances.
And while Kendall, who recently posted racy photos on her own Instagram account, isn't shy about getting attention, she seems to want to keep this part of her love life private – for now.
"I'm sure everything they do goes through Kris," says the source close to the couple. "It has to be approved or it's pre-planned and well thought out. But I think you'll see a lot more of them soon."
Reps did not respond to requests for comment but Jenner Tweeted a message Thursday: "enough with the rumors! I'm single, people," she wrote with a smiley face.