On Thursday, the musician, 33, tweeted that he and the Sixteen Candles alum locked eyes at a film screening.
“Made eye contact with Molly Ringwald at a Love Simon screening!” Antonoff shared about Ringwald, 50.
Among the Twitter users who responded was Dunham, who has a close connection to Ringwald.
“You’re aware she and my mom are best friends, right?” Dunham, 31, replied. “It’s stunning.”
“I was gonna bring it up! i didn’t!” he tweeted in response.
After five years together, the former couple amicably parted ways, PEOPLE reported in January.
The Girls creator and Bleachers frontman met on a blind date set up by Antonoff’s sister and comedian Mike Birbiglia in 2012. The first date went so well, the guitarist quickly told Dunham everything about himself, “because when you really like someone, you want them to know everything about you,” he told New York in 2014.
Despite their split, Dunham still holds a special piece of Antonoff close to her.
Following their breakup, Dunahm showed off her rings — one of which was a gift from Antonoff — on an Instagram livestream.
“I’m wearing this ring that Jack gave me, and I’ll always wear it because love is a really cool, powerful, eternal thing,” Dunham said about the jewelry. “It doesn’t have to be defined the way that we, in Western culture, define it as beginnings and ends.”
“Things can be, ‘You know what, you’re a drop of water, and then you reenter the ocean.’ Anyway, I really love you all,” she continued. “I’m really thankful for the support. I’m really thankful for the love.”
“My beautiful partner, who has seen me through so much pain with compassion and care, has to be away for work, and I can feel us growing slowly apart, since life is so determined to display its full complexity right now,” she wrote in an essay for Vogue. “I am surly and distant. I offer nothing.”
“He reminds me again and again that I am still a woman and still alive,” she continued. “But I also know that soon — for so many reasons that have nothing to do with my uterus — we’ll slip away from each other and I will face everything I am losing in impossibly tiny steps.”