Jennifer Garner's 'Love Triangle': Actress 'Driving Away New Boyfriend' By Being Ben Affleck's 'Rock' Amid His Bitter J Lo Divorce Battle

Three's a crowd for John Miller — who is said to be struggling with his girlfriend Jennifer Garner's flooding support for her ex-husband.

Jen has been a rock for Ben Affleck during his divorce from Jennifer Lopez, but John is growing impatient with her split focus, RadarOnline.com can reveal.

A source disclosed that the 46-year-old businessman has felt uneasy about his girlfriend "running to Ben's side" since the actor's split from J Lo, who filed for divorce in August.

They said: "John's argument is that Ben's an adult and should figure it out without impinging on their life."

The 13 Going on 30 star's divorce from Affleck, finalized three years after their 2015 split, ended a tumultuous romance marked by his struggles with substance abuse and gambling.

Miller, who Garner began dating in 2018, brought stability to the star's life — as they have kept much of their "quiet" relationship out of the public eye.

But Garner, who shares kids Violet, 18, Fin, 15, and Samuel, 12, with the Argo star, has consistently extended extra grace to her troubled ex.

She said after their divorce: "He's the most brilliant person in any room... he's just a complicated guy."

Now that Affleck has split from Lopez after two years together, Garner has shown up for him as a close friend and confidant.

The source added: "Jen feels a sense of responsibility to Ben. But John wants to marry her — and he feels there should only be two people in a marriage, not there."

Affleck and Lopez initially met in 2002, got engaged, and broke it all off in 2004. They rekindled nearly two decades later and tied the knot inside a Las Vegas chapel in July 2022.

While Affleck and Lopez were seen together on several occasions this summer, including on Affleck's 52nd birthday, J Lo filed for divorce in Los Angeles on August 20.

The pair were spotted out together just one month later, but a source insisted the former couple were "still moving forward" with their divorce.

Last week, insiders claimed Affleck "never looked back" after calling it off with the Marry Me star.

They also said the Oscar-winning actor didn't fret over his decision to move out of their shared $68million home and that he's been "very focused on work and his kids" as a newly single man.

The former couple listed their marital home for sale in June — a little over a year after they bought the estate in May 2023.

Since then, Affleck has moved out of his rental home and into a $20million bachelor pad, which he purchased in July.

In her cover story for Interview Magazine, Lopez recently opened up about how dramatically her life changed in a matter of months.

She said: "The work is figuring yourself out. It's looking back at the feelings underneath and the belief systems that we have about ourselves that make us make certain choices and create certain patterns in our life."

The 55-year-old added: "But you have to be healthy. You have to be complete, if you want something that’s more complete. You have to be good on your own."

"I thought I learned that, but I didn't. And then, this summer, I had to be like, 'I need to go off and be on my own. I want to prove to myself that I can do that.'"

While Lopez said her summer felt "lonely, unfamiliar, scary, sad, and desperate," she also noted how being in a relationship isn't what "defines her".

Have a tip? Send it to us! Email RadarOnline.com at tips@radaronline.com.