"They're dating -- it's been at least a few months," a source close to the couple toldPeople. "They've been getting closer recently, and they've been hanging out all the time."
While their relationship has been hush-hush since they began seeing each other this past summer, Jenner reportedly plans to go public with her romance following her 18th birthday on November 3.
"They have that spark right now -- they're just really feeling each other," said the source. "They're not putting it out there yet... I'm sure everything they do goes through [momager Kris Jenner]. 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."
"He's so sweet. 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," added the source.
The rapper recently posted a photo on Instagram of what appears to be a silhouette of himself with Kendall, who is making a heart shape in the sky with her hands at sunset. Kendall's sister Kylie Jenner, 16, posted the picture on her Instagram account as well, and she's friends with Jaden Smith and rapper Lil Twist -- who are both boys with Jinsu.
While the couple is reportedly dating, they apparently haven't reached official boyfriend/girlfriend status yet.
"Enough with the rumors! I'm single, people," Kendall tweeted Thursday.