Ben Affleck and Jennifer Lopez are trying to keep their divorce civil ... attending the same event with their fam -- including Ben's ex Jennifer Garner!

The trio stepped out Friday night in Brentwood ... hitting an event in the West Los Angeles area -- and, though we don't know if they actually had a convo -- we do know Ben and J Lo arrived just minutes apart.

We're told Garner arrived first at around 7 PM ... with J Lo following her five minutes later and Ben pulling up shortly after that.

All three appear to be in good spirits while out in the affluent West L.A. neighborhood ... with Affleck and Garner seen walking together.

While we don't know if the threesome chatted during the evening ... clearly, Ben and Jenn G. chatted on their way inside, but it seems less likely Bennifer met up for a convo given the fractured nature of their relationship.

As you know ... J Lo filed for divorce from Ben in August -- sans lawyer. The two don't have a prenup, and they've worked together on multiple projects during their marraige, so it'll be a complicated split.

Laura Wasser -- the disso queen - is mediating the divorce ... just like she mediated Affleck and Garner's back in 2018.

After the split, Lopez told comedian Nikki Glaser that being in a relationship shouldn't define her ... and. she's looking forward to being on her own.

They may no longer be together, but looks like Affleck and Lopez won't be able to stop running into each other anytime soon.