The couple has been dating on-and-off since 2018.
Jennifer Garner's relationship with John Miller is thriving. A source tells ET that The Last Thing He Told Me star and her beau, who were recently spotted out on a run together, are "doing great" amid their romance.
"Jen is a fantastic mom and she is always trying to stay positive and put her family first," the source says of Violet, 17, Seraphina, 14, and Samuel, 11, the three kids Garner shares with her ex, Ben Affleck.
"John appreciates how dedicated Jen is as a mom and has so much respect for her," the source adds of the couple, who kept things casual during their Los Angeles, California, jog on Monday.
Garner and Miller have been dating on-and-off since 2018. Back in January, Miller was spotted having a friendly chat with Affleck, who's currently married to Jennifer Lopez. Shortly thereafter, a source told ET that the two men get along well.
"Ben is very supportive of Jennifer dating and just wants her to be happy. It's important for Ben to have a solid relationship with John," the source said. "Ben is so laid-back and gets along with everyone, and John is one of those people too."
"John's a cool guy, down to earth, and likes Ben too," the source added. "They don't hang out much on their own, text, or anything like that, but they have no issues when they are together. Ben has moved on and is very happy with Jen. He wants the same for Jennifer and nothing but the best for her."
As for how Garner and Lopez feel about each other, a source told ET in June that the women "are very cordial and they have a very healthy and functioning relationship."
The source added that their kids -- including Lopez and Marc Anthony's 15-year-old twins, Max and Emme -- are also getting along well and "learning and growing together as a new, extended family."
The source noted that the 13 Going on 30 star is in "a great space and feels good about where things currently stand with the new family dynamic."
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