The singer announced her engagement to the actor over the weekend.
"They feel like they are living their dream life," the source says. "Ben always knew he wanted to marry Jen and they are so excited and happy."
Affleck and Lopez previously got engaged in 2002, when he proposed with a memorable pink ring, but they called it off in 2004. They rekindled their romance in February 2021, after Lopez's split from Alex Rodriguez.
Lopez, 52, shared the news about her and Affleck's second engagement in her newsletter on April 8. In a video, Lopez fought back tears as she showed off her stunning green ring and said, "You're perfect."
The announcement came after the singer sparked speculation that she and Affleck, 49, were engaged when she stepped out wearing a ring on that finger.
Last month, a source told ET that an engagement was an "ongoing conversation" between the couple.
"Ben and Jen can't wait to spend the rest of their lives together and know that they were destined to be together," the source said. "Jen and Ben are incredibly supportive of each other. Ben is Jen's number one fan and he completely champions her and always tells her how great he is. He loves talking about her different projects. She is a huge supporter of his too, but Ben really can't stop telling everyone how smart and hardworking she is."
"They actively talk about what didn't work in the past and use those experiences to strengthen their relationship now, for the future and for the sake of themselves and their families," the source continued. "They are committed to having a healthy, everlasting relationship."