Well, such speculation has surfaced after the two were seen arriving, albeit separately, at SilverCup Studios in Queens, New York, on Monday.
"Justin came to the studio, then Kendall arrived a little bit later to the same studio," a source tells E! News. "They stayed for a few hours."
The eyewitness added that that the 20-year-old pop singer arrived to the studios through the garage, while the 18-year-old Keeping Up With the Kardashians star walked in through the front door, completely alone, soon after him.
Our source believes they left separately as well.
The sighting comes just one day after there were reports the two were going to star in the next Calvin Klein campaign.
However, a source informed E! News that there's no truth to the rumor that that they are teaming up for the fashion brand.
Also, Calvin Klein's spokesperson told us that "as a policy we don't comment on rumors."
Guess time will tell what brought them together yesterday.
—Reporting by Lindsey Caldwell