Sources with direct knowledge and connection to both Kylie and Travis tell TMZ ... they have rekindled the old flame and are dating again, but they're also free to date other people. To be blunt ... they are in an open relationship.

We're told ever since the 2 broke up in late 2019, Travis has been enjoying the bachelor lifestyle and all that comes with it ... but he also wanted to get back with Kylie and be a strong family unit.

So, we're told they've agreed to get back together but with a non-exclusive couple arrangement ... and both are cool with that.

We broke the story ... the couple took their daughter, Stormi, to Disneyland Tuesday, adding to all the recent signs they're together again.

Before that, they did a triple date night with the Biebers and Kendall Jenner and Devin Booker, which was not long after the big news that Kylie flew to Miami to celebrate Scott's bday with him.