Kendall Jenner and Justin Bieber have been rumored to be dating on and off since 2014, but it's never been confirmed. In 2016, Kendall was asked about the rumors during an interview with Ellen DeGeneres and she said, He's a longtime friend of our family. I've known him since I was so young—he used to come over and he'd play with Kourtney and Kim's kids all the time. He's great.
So, it seems like Kendall and Justin are just friends, despite what the tabloids might say!