The source also tells ET that Jennifer Garner and Marc Anthony continue to be 'supportive' of their exes' relationship.
"They have insane, on another level, chemistry. They are both super passionate and are head over heels with each other, just like they once were," the source says. "This time around, however, they both really feel like this is it."
The source adds that "everything feels 100 percent natural with them. Once they rekindled, it was like no time had passed."
"They couldn't be more in agreement. They feel at this point in their lives they were undeniably made for each other," the source continues. "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."
"Nothing has been supremely difficult, and they don't tend to bump heads. They are always working as a team and they love that about each other and their relationship," the source notes.
Lopez was previously married to Marc Anthony from 2004 to 2014. They share 13-year-old twins Max and Emme. As for Affleck, he and Jennifer Garner were husband and wife from 2005 to 2018. They are parents to daughters Violet, 15, and Seraphina, 12, and son Samuel, 9.
Lopez and Affleck maintain friendly relationships and co-parent with their exes. The source tells ET, "Jen Garner and Marc Anthony are continuing to be supportive and there doesn't seem to be any ill will across the board. They all just want what's best for each other and their families."
As for Lopez and Affleck's kids respectively, the source says, "Their kids just want to see their parents happy and they are what is most important to both of them. J.Lo's kids are so glad to see their mom so in love."
Lopez and Affleck, meanwhile, have been enjoying a PDA-filled vacation in Europe as they celebrated the Hustlers' star's 52nd birthday. Fans were overjoyed to see J.Lo make their relationship Instagram official, wearing a necklace reading "BEN," and both of them giving off "Jenny From the Block" vibes on a private yacht.
For more on their romantic getaway, watch the video below.