Jennifer Grey said she had a 'secret rendezvous' with Matthew Broderick while they were filming 'Ferris Bueller's Day Off'

• "Ferris Bueller's Day Off" is celebrating its 36-year anniversary on June 11.
• On-screen siblings Matthew Broderick and Jennifer Grey publicly dated in real life after filming.

In her critically acclaimed memoir, "Out of the Corner," Jennifer Grey said she had a "clandestine set romance" during "Ferris Bueller's Day Off" with her on-screen brother played by Matthew Broderick.

"I was as surprised as anyone when our relationship morphed from on-screen sibling rivalry to off-screen illicit romance," Grey wrote.

The wildly popular comedy "Ferris Bueller's Day Off" was released on June 11, 1986.

The film follows optimist Ferris (Broderick), who pretends to be sick and skips school so he can gallivant around Chicago with his friend Cameron (Alan Ruck) and girlfriend Sloane (Mia Sara). Meanwhile, his brooding sister Jeanie (Grey) attempts to prove he's playing hooky throughout the film.

Grey and Broderick publicly dated after filming, but the actress shared in her new memoir that they had a "secret rendezvous" while filming and hid it from the cast and crew.

"Suddenly you're living one of those bedroom farces, padding down the carpeted hallway, barefoot in your robe, or in various stages of undress," Grey wrote about staying discreet while everyone lived together in the same hotel during filming. "The row of peepholes on the other guests' doors can feel like an army of eyeballs watching your every move."

On one occasion, Grey recalled being in Broderick's room and the actor's "sudden change in demeanor" when he bolted up and signaled for her to be quiet when he received a phone call.

"There appeared to be some girl he had failed to mention, who was or was not, in fact, his girlfriend," Grey wrote, adding, "When I questioned him about this mystery woman, he assured me she was not his girlfriend but more of a close family friend who fancied him."

Grey said while she considered herself a "girl's girl," she was in denial of there potentially being another woman — or herself being the 'other woman.' "It boiled down to: I wanted what I wanted," she said.

The actors continued their affair until filming ended and they parted ways temporarily.

After being back home in New York, Grey remembers, "I realized I was in love with Matthew and told him I couldn't see him anymore. He promptly broke up with his 'close family friend' and we were together."

"Matthew just felt like my guy," Grey said, also adding, "He felt like home."

The couple dated and were briefly engaged in 1988. Grey recently said in an interview with Drew Barrymore that she went from being engaged to Broderick and splitting up with him to then being engaged to Johnny Depp all in the same month.

Broderick has not responded to Insider's request for comment.

"Out of the Corner" is available now.