Blake Lively's sister Robyn has also worked with Ben Affleck: See the epic throwback photo

Long before Ben Affleck and Blake Lively had an onscreenromance in the film The Town, the hunky dad-of-three shared the screen with the Gossip Girl alum’s older sister Robyn Lively.

Back in the early ‘90s, the Argo actor and Robyn had roles on the NBC drama television series Against the Grain. The two played siblings on the show, whichwas about their football star father coaching a high school team.

Robyn captioned the major throwback, “Before #BenAffleck was Batman he was just my darling brother in a series called #againstthegrain #3degreesofbaconAffleck.”

Ryan Reynolds' wife and Ben went on to star nearly 20 years later inthe 2010 drama The Town, where they shared a steamy sex scene. Discussing the scene, which occurred on Blake's first day on set, Ben admitted, "[She was] very poised and comfortable about it - more mature than some of the crew members."

The actress credited her family for that. "Well, I have a big family and no one ever treated me like a child," she explained. "They always treated me like an adult, like an equal. But with acting, I think half of it is just acting confident. We stand on these red carpets and pose in these dresses, but we're all only so confident. It doesn't mean we think we're great looking or anything. It's all a facade. But the sex scene was really awkward. It was my first day.”

Blake Lively and Ben Affleck at The Town press conference during the 2010 Toronto International Film Festival Photo: Getty Images

Ben, who stars in the upcoming Batman v Superman: Dawn of Justice, recently celebrated his son Samuel's fourth birthday with ex-wife Jennifer Garner. The former couple's son requested that his father wear his Batman costume for the festivities.

"I was like okay. I had to call the studio and say, 'Is there any chance someone has the costume around?'" the 43-year-old said, though he admitted the studio was initially hesitant to loan him the suit. He laughed, "They trust me for the movie, but not for a four-year-old's birthday.”

The actor added that at the party, "There was Wonder Woman, Captain America, Iron Man and there was me. It was so mortifying ... I didn't think that all the kids' parents would be there. It's 11 in the morning and [the parents] are like, wow, Batman!"

Batman v Superman: Dawn of Justice opens in theaters March 25.