Brody Jenner and Kaitlynn Carter Co-Parenting Dogs, Not Back Together

Brody Jenner and Kaitlynn Carter may SEEM like they're rekindling a lost romance, but they're not getting back together ... instead, they're just co-parenting pooches.

Here's the deal ... fans have noticed Brody and Kaitlynn lookin' pretty chummy recently -- BJ was the muscular hunk in the reflection of one of KC's snaps, and they both posted similar photos from the same beach -- but we've learned there's nothing brewing, other than a new dog in the mix.

Sources close to the famous exes tell TMZ ... Brody and Kaitlynn have hung out and bumped into each other a few times, but it's NOT a sign they're getting back together.

When Brody and Kaitlynn were "married" -- it was never a real marriage, there was a ceremony in Indonesia but they never made it legal -- they shared 3 dogs together ... Radar, Tank and Shoey.

Our sources say Brody and Kaitlynn had an agreement when they split ... he would take the dogs full time, and she had visiting rights.

We're told Kaitlynn adopted a new dog, Dash, a couple months ago and wanted to introduce the pup to the pooches she co-parents with Brody, so the exes set up a meet-and-greet for the dogs.

They all hit it off -- the dogs, not Brody and Kaitlynn -- freaking out and playing like good boys and girls.

Brody and Kaitlynn are getting along too ... we're told they said hello and were friendly when the bumped into each other at the beach in Malibu, in what sources say was not a scheduled hangout.

The exes are both moving on, but we're told there's no bad blood ... Brody was spotted quarantining with a UCSB grad and witnesses say Kaitlynn went on a date this week with Amber Heard's ex, Kristopher Brock.