Not again. On October 18, Ben Affleck arrived at his children’s Los Angeles school for an evening event with his 15-year-old child, Fin. Looking like the ideal coparents, he and ex Jennifer Garner walked in as a family.

On the same night, however, Ben’s second ex-wife, Jennifer Lopez, was also in attendance alongside 16-year-old Emme, her child with ex Marc Anthony. That reunion (or nonreunion; the two groups stayed separate) was icier. “Ben knows he’s going to see Jen at these functions. Their kids go to the same school, so how could he not?” a source exclusively tells In Touch. “Still, it’s awkward.”

The run-in was one of several the former couple have had in the two months since Jen filed for divorce after two years of marriage. In mid-September, they brunched together at the Beverly Hills Hotel with Fin as well as Ben’s son, Samuel, 12, and Emme’s twin brother, Max. (Their children became close while Ben and Jen were married.) Just three days after that, Ben, 52, and Jen, 55, were both at their kids’ back-to-school night.

Like many divorced couples, the Argo director and the Shotgun Wedding actress keep finding themselves thrust into situations together, like it or not. “Ben would rather not see Jen, but the kids come first,” says the source. “He can’t be selfish.”

Jennifer Lopez Can’t Let Go

J. Lo says she’s focused on moving on. In a recent sit-down with Interview magazine, she opened up about making peace with the painful split from the man of her dreams. “It was like my whole f-king world exploded,” she said of the breakup, adding that the experience forced her to face her fears about being alone. “You have to be complete, if you want something that’s more complete,” she explained.

The singer shared that her wisdom was hard-won. “You have to be good on your own,” she explained, adding that it took a solo summer of self-exploration for her to “prove” to herself that after the demise of her fifth marriage, she was content to be alone. “Being in a relationship doesn’t define me. I can’t be looking for happiness in other people. What if I’m just free?”

Yet, as In Touch has previously reported J. Lo has been enjoying a few rebound flings, and the insider says, “This is not where she saw herself at 55.” Constantly running into her ex- especially looking so happy with his confidante Jen Garner – is a cruel reminder of that.

Jennifer Garner Is the Middle Woman

For Ben, the contrast between J. Lo and Jen G., also mom to Violet, 18, couldn’t be more stark. “She’s a stabilizing influence, and she’s been a huge support throughout his split,” says the insider. “They’re the best of friends and there’s no awkwardness between them.”

Jen has been a rock through his struggles with sobriety, even driving him to rehab after their split. J. Lo, on the other hand, with whom he shares no kids, has less of a hold on him moving forward. Not that that’s what the This Is Me… Now star is hoping for. “She’d like to be closer,” adds the source, “but as far as Ben’s concerned, it’s better for them to keep separate lives as much as possible.”

There’s only so much they can do to avoid each other — for now. “It’s not like they’re not going to pull their kids out of school,” says the source. Their upcoming film project, Unstoppable (produced by Ben and starring Jen), is due out in early December and may also force them to spend more time together.

They’re making the best of a tricky situation. “Ben and Jen are resigned to keeping things as is,” says the insider. “The hope is it’ll get easier as time goes by.”