"Love you love you love you love you 1/30/2021," Kopelman captioned a black-and-white picture, in which the actor kissed his new fiancée on the cheek, while Michler showed off her engagement ring.
"So amazing!!" one fan gushed.
"Yay!!! Sending all the love," another wrote.
"Some joyful news in endless January! ECSTATIC for my fabulous *engaged* brother @willkopelman and his incredible bride-to-be! Sooo lucky to have you as my sis-in-law @alliemichler," Kopelman’s sister, Jill Kargman, wrote on Instagram, alongside the same snap her brother shared.
"Thank you Jill!!!! Beyond happy and so happy to have you as my sis in law!!!!!" Michler replied in the comments section.
Kopelman’s father, Arie L. Kopelman, who is the former CEO and President of Chanel, also took to social media to gush over the good news.
"SO thrilled that our son Will and Allie are engaged - - two such special people! We’re all beyond excited - - what a blessing to share such great news in these difficult times!" he captioned a picture of his son and the bride-to-be holding champagne glasses.
Kopelman got married to Barrymore in 2012, but they divorced in August 2016.
"Sadly our family is separating legally, although we do not feel this takes away from us being a family," they wrote in a joint statement at the time. "Our children are our universe, and we look forward to living the rest of our lives with them as the first priority."
Barrymore opened up about their co-parenting relationship in 2018 and recalled reading an article that said she had gotten her happy ending but "many times in life for all of us, our plans change and our dreams are adjusted," she wrote in an Instagram caption.
"But that doesn’t mean that every second wasn’t worth it. And if that DeLorean time machine pulled up every day, I would do it all over again. After all, I did get my dream. 2 healthy girls. Will and I continue to marvel at what we made and try to be the best coparents we can be. It’s not always easy and the point is…nothing in life is. But it doesn’t mean that any bitter outweighs the sweet!"
In October 2020, the actress shared more and revealed she didn’t take the divorce well at the time.
"I know from not growing up with any family whatsoever that that was the last thing that I wanted to do for my daughters. I think that’s why I took it so hard. It was, like, ugh the ultimate promise I wanted to make with you and for you was to have this amazing family and I found that and there’s something not working, that isn’t livable. How tragic is that?" Barrymore tearfully said on the Today show.
Kopelman was Barrymore’s third husband — she was married to Jeremy Thomas from 1994-1995 and to Tom Green from 2001-2002. Before she tied the knot with Kopelman, she dated Fabrizio Moretti for five years.
Barrymore and Kopelman share daughters — Olive, 8, and Frankie, 6.