Kendall Jenner and Devin Booker are rekindling their relationship, but they're taking things slow -- and they're not even exclusive just yet ... TMZ has learned.

Sources familiar with the situation tell us the former lovebirds have been spending more time together lately -- something that became evident during the Super Bowl ... when DB popped up in the Kardashian suite super randomly, albeit separated from Kendall.

Still, it was curious ... and obviously sparked new dating rumors about them -- this after spending just about all of 2023 apart.

Remember, she was dating Bad Bunny at the time ... and they were quite serious.

Anyway, our lying eyes weren't deceiving us -- as it turns out ... we're being told they are, in fact, seeing each other again -- but our sources emphasize they're not rushing into things.

Eyewitnesses tell us they've even seen Kendall pop up in Dallas this week while Devin was in town for the Mavs/Suns game Thursday -- so yeah, she's even traveling to be with him lately.

It's interesting that they're circling getting back together ... they first broke up at the end of 2022, and according to reports -- it was apparently all over how busy they were and not having time in their schedules to keep it going as a couple.

Considering they're both just as famous (if not more so) since then, that rationale sounds like BS -- Devin is still a pro basketball player, and she's still a super successful model.

And yet ... somehow they're finding time to hang/bang right now. Welcome back, y'all!