Jennifer Garner’s boyfriend, John Miller, issued an ultimatum after Ben Affleck was spotted getting cozy with his ex-wife, a source exclusively tells Page Six.

The CaliBurger CEO “has always been supportive of Ben and Jen’s co-parenting relationship but feels Ben crossed the line,” the insider says.

“John knows there’s nothing going on between Jen and Ben, but he doesn’t think those photos are a good look and feels it’s disrespectful to their relationship.”

Jennifer Garner’s boyfriend, John Miller, issued an ultimatum after Ben Affleck was spotted getting cozy with his ex-wife, a source exclusively tells Page Six.

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The CaliBurger CEO “has always been supportive of Ben and Jen’s co-parenting relationship but feels Ben crossed the line,” the insider says.

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Miller’s proposal comes after the “Gone Girl” star was seen affectionately grabbing the “13 Going on 30” actress as the couple celebrated their son Samuel’s 13th birthday on March 2.

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According to the source, Miller “gave Jen an ultimatum” — “he doesn’t want to see anything like that again or he has no choice but to walk away.”

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Affleck pulled Garner in toward him, and she appeared to welcome the embrace.

The “Daredevil” co-stars — who also share Violet, 19, and Seraphina, 16 — looked cozy as they laughed and closely chatted while participating in the festivities.

Reps for Miller, Garner and Affleck did not immediately respond to Page Six’s requests for comment.

The “Daredevil” co-stars looked cozy as they laughed and closely chatted while participating in the festivities.

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