Lopez shared the news in her On the JLo newsletter days after she was photographed wearing what appeared to be an engagement ring earlier this week.
The message to fans included a clip of Lopez admiring a huge, green diamond on her ring finger, an image of which was also shared by her sister on social media.
Lopez teased the "major announcement" with a video on Twitter that same night. "So I have a really exciting and special story to share..." Lopez told her followers
Lopez recently told what makes their connection different now compared to 18 years ago, saying, "We're older now, we're smarter,
The Marry Me actress, shares 14-year-old twins Emme and Max with ex-husband Marc Anthony, and Affleck, shares three kids with ex-wife Jennifer Garner: Violet, 16, Seraphina, 13, and Samuel, 10.
It's a beautiful outcome that this has happened in this way at this time in our lives where we can really appreciate and celebrate each other and respect each other
"We always did, but we have even more of an appreciation because we know that life can take you in different directions."
She added, "We have been in the game in the public eye long enough to know who we are as people and what really matters and what doesn't matter
We have kids and we respect each other. ... We really live our lives in a way we can be proud of and our kids can be proud of you.
Lopez and Affleck previously began dating in July 2002 and got engaged that November before postponing their September 2003 wedding just days before the date
Moses J. Moseley, known for his role on "The Walking Dead," died from a gunshot wound to the head, according to his autopsy.