Juliano/X17online.com Jennifer Garner and John Miller's relationship is stronger than ever, a source tells PEOPLE The CaliBurger CEO is "deeply respectful" of Garner's relationship with her ex-husband, Ben Affleck Garner and Miller have quietly dated on and off since 2018 Things betweenJennifer Garnerand longtime boyfriendJohn Millerare "better than ever," a source tells PEOPLE exclusively. The13 Going on 30actress and Miller —who have quietly dated on and off since 2018— "hit a stride as a couple and those who know them say this is the most solid and connected they've ever been." Garner, 53, shares three children with ex-husbandBen Affleck, 52. The former couple was married for 10 years, from 2005 until 2015. MLB/X The exes have long prioritized a healthy co-parenting relationship, which is something Miller — a businessman who is best known as the chairman of a technology company called CaliGroup, which owns the CaliBurger restaurant chain — fully supports. According to the source, "John has also embraced Jen's family life. He's been patient, supportive and deeply respectful of her dynamic with Ben and the kids." Garner and Affleck were recentlyspotted watching the Boston Red Soxtake on the Tampa Bay Rays at Fenway Park on Friday, July 11. Jim Spellman/WireImage Two of the former couple'schildren— Seraphina, 16, and Sam, 13 — were also present for the game night. Affleck and Garner's eldest child, 19-year-old Violet, was not in attendance. TheArgoactor and theDaredevilstar were deep in conversation when Affleck seemed to notice the attention on them as he nudged Garner, who flashed a smile in the direction of the camera seconds later. Meanwhile, Garner and Millershowed off some PDAwhile attending the67 Strong: Jen Garner's Final Mile 4 Kidsevent in Santa Monica, Calif. on June 22. TheSave the Childrentrustee and ambassador completed the final installment in her 67-day challenge of running one mile a day to benefit#67Strong4Kids. Garner got some love from longtime beau Miller, who planted a kiss on the actress following her final mile. Read the original article onPeople