"Ben has always had an affinity for Jennifer and was the one who initially started pursuing her and making an effort to reconnect, romantically speaking," the source says. "He wanted to explore things with her beyond a friendship and they've both really been enjoying spending time together."
A source also tells ET that things between the two took a romantic turn in February.
"Jen and Ben have remained in contact since their breakup and would see each other from time to time, but as friends," the source says. "In February things took more of a flirty turn. Ben started to pursue Jen and made it clear he wanted more than a friendship. The two have always shared a strong bond and are spending time together to see if there is a spark or it's just two friends finding comfort in one another."
According to a TMZ report, Affleck started reaching out to Lopez in February while she was filming Shotgun Wedding in the Dominican Republic and continued to email her until the shoot ended in April. Sources told the outlet that his emails were more than friendly and referenced her love for his writing, including a line about him being able to "own her heart" with his pen.
"They have a good time when they're hanging out and things have been easy, fun and exciting between them," the source said. "They've stayed in touch over the years, so the two of them reconnecting isn't a huge surprise to their friends. Ben is protective over J.Lo and they're trying to be as low key as possible."
Affleck did make his admiration for Lopez known in April, when he gushed about her in honor of her May cover of InStyle.
"I don't know whether people know it or not, but the most impressive thing about her (and that is a long list) was her extraordinary work ethic," he told the magazine. "She had this humility coupled with the basic assumption that not only did you have to work incredibly hard to succeed, you had to then push yourself even further."
"I thought I had a good work ethic, but I was completely humbled and blown away by what she was committed to doing day in and day out, the seriousness in which she took her work, the quiet and dedicated way she went about accomplishing her goals, and then how she would go back and redouble her efforts," he continued. "She remains, to this day, the hardest-working person I've come across in this business. She has great talent, but she has also worked very hard for her success, and I'm so happy for her that she seems, at long last, to be getting the credit she deserves."
He also pointed out her ageless looks.
"Where are you keeping the fountain of youth? Why do you look the same as you did in 2003 and it kind of looks like I'm in my 40s…at best?" he joked.
And it seems Affleck's loved ones are all for him reuniting with Lopez. His best friend, Matt Damon, was asked about Affleck and Lopez's headline-making reunion during his appearance on the Today show on Monday, and he commented, "I love them both. I hope it's true. That would be awesome."
"She wants what is best for Ben," the source said. "What matters most to her is Ben being a great dad. They've been in a good groove when it comes to co-parenting for a while and their kids' happiness is Jen's main priority."