A source tells ET that the 52-year-old entertainer attended a star-studded event at producer Jennifer Klein's house over the weekend, and handpicked out necklaces for Violet, 15, and Seraphina, 12. Affleck also shares 9-year-old son Samuel with ex-wife Jennifer Garner, while Lopez has two kids, 13-year-old twins Emme and Maximilian, with ex-husband Marc Anthony.
"While there, Jennifer checked out the Made by Mary station and picked out necklaces for herself and Emme, as well as Ben Affleck's daughters, Violet and Seraphina," the source says. "The necklaces Jennifer picked out are from the brand's birth flower collection and she selected a July Lotus, February Violet, December Holly and a January Carnation to match their birthday months."
"Jennifer mentioned that she planned to gift Violet and Seraphina the necklaces later that night," adds the source, "at Ben's 49th birthday celebration."
Lopez has also been sporting sentimental jewelry of her own these days. In recent months, the "Let's Get Loud" singer has been spotted out multiple times wearing a "BEN" necklace, symbolizing her love for the actor.
"They have insane, on another level, chemistry," an additional source told ET of Lopez and Affleck's reignited romance. "They are both super passionate and are head over heels with each other, just like they once were. This time around, however, they both really feel like this is it."
"They couldn't be more in agreement. They feel at this point in their lives they were undeniably made for each other," the source continued. "Things between Ben and Jen have been easy and that's what makes their relationship work so well. They work seamlessly together and it's like their relationship hardly takes any effort."
Meanwhile, Lopez's ex, Alex Rodriguez, has been embracing the single life. Just weeks after celebrating his 46th birthday aboard a yacht with family and friends, the former MLB star sat down with ET to discuss his new Presidente beer venture. He also opened up about how he's in a "great place" following his highly-publicized split from Lopez earlier this year.
"I had five years of an incredible life and partnership and also with my daughters, we learned so much. And now we have the opportunity to take that and move forward and say, 'You know what? We're so grateful for the last five years, how do we make the next five years better because of lessons learned?'" he shared. "So I'm in a great place. I'm so grateful for where God and and and the light has really put me, and I'm really looking forward. Mostly to see how my girls keep developing."