After being with Al Pacino for a while, Diane Keaton desired more commitment in their relationship. However, Pacino wasn't willing to take the next step of marriage for a valid reason.

In Diane Keaton's book, "Then Again," the actress revealed how she'd first met Al Pacino at 'O Neals' bar near the Lincoln Center. The meeting was to allow the two stars to get to know each other better before auditioning for "The Godfather."

Keaton was nervous, and the first thing she noticed about Pacino was his nose, which she likened to a cucumber with Roman features. She also picked up that he was nervous too, and she didn't recall discussing the script.

Diane Keaton and Al Pacino starring in "The Godfather," in 1972. | Source: FilmPublicityArchive/United Archives/Getty Images

The actress thought Pacino had a "remarkable face." She ended up finding out that he wasn't available, but it didn't matter because she wasn't too; however, she yearned for him, stating:

“For the next twenty years Al Pacino would be my only recurring 'unattainable great.'”

FALLING IN LOVE WITH AL

Diane Keaton and Al Pacino at the screening of his movie, "Sea of Love" on September 12, 1989. | Source: Robin Platzer/Getty Images

Keaton somehow managed to get closer to Pacino by offering to teach him how to drive. The driving lesson took place in Lake Tahoe in the Cal-Neva Hotel parking lot, where Pacino struggled to locate the brakes.

He also couldn't distinguish between the right and left signal lights. Pacino also kept pushing the gas no matter how many times his instructor informed him that the brakes were for stopping, leading Keaton to laugh.

Al Pacino posing in a black and white photo in 1974. | Source: Hulton-Deutsch Collection/CORBIS/Getty Images

Another strange thing about Pacino was how he didn't like going out and eating with other people. He preferred being alone at home, eating while standing, and didn't get why people sat around tables and conversed; in her book Keaton shared her love for him, saying:

“Recently I went to a screening and fell in love with Al all over again. The whole package.”

Diane Keaton as Kay Adams in "The Godfather," with the release date of March 15, 1972. | Source: CBS/Paramount Pictures/Getty Images

In 2017, the actress confessed her true feelings for Pacino to People magazine, revealing how she'd "had a crush" on him in 1971 while they were working together on "The Godfather." After they became a couple, Keaton admitted this about him:

“I was mad for him. Charming, hilarious, a nonstop talker.”

Al Pacino during the American Film Institute's 45th Life Achievement Award Gala Tribute to Diane Keaton on June 8, 2017, in Hollywood, California. | Source: Kevin Winter/Getty Images

She thought he had an aspect that made him seem like a lost orphan. The Lifetime Achievement Award winner said he was like a crazy educated person or distinguished scientist and quite gorgeous!

During 2017's American Film Institute (AFI) ceremony, where Keaton received her Lifetime Achievement Award, Pacino discussed their relationship. He recalled an incident where he was nervous before an interview, and the actress encouraged and supported him.

The hilarious advice she gave him before he left the house was not to call himself an artist during the interview! Pacino confessed that it had been good advice and concluded his speech by praising Keaton for her acting skills.

THE ULTIMATUM DIANE GAVE TO AL

Al Pacino as Michael Corleone and Diane Keaton as Kay Corleone on "The Godfather, Part II," in 1974. | Source: FilmPublicityArchive/United Archives/Getty Images

Keaton and Pacino managed to pursue a relationship for several years, but it failed to go anywhere. At one point, the actress pushed her boyfriend by giving him an ultimatum, which led to the demise of the relationship, with Keaton confessing:

“I worked hard on that one. I went about it in not a perfect way.”

Al Pacino as Michael Corleone and Diane Keaton as Kay Corleone on "The Godfather, Part II," in 1974. | Source: FilmPublicityArchive/United Archives/Getty Images

The fallout happened in Rome while the couple was in the middle of shooting "The Godfather III." Keaton said to him, "Marry me, or at least commit to the possibility," and they broke up before getting back together again.

Pacino didn't want marriage, and his girlfriend kept insisting on it. After breaking the relationship up a dozen times, the pair called it quits again and couldn't even greet; two months after Keaton's father died, Pacino made a confession, with the actress recalling:

“Al admitted in the safety of the therapist’s office what I must have always known: He never had any intention of marrying me. What he wanted was out.”

Diane Keaton at the L'Oreal Paris' Women of Worth event on December 3, 2013, in New York City. | Source: Fernanda Calfat/Getty Images

During a 2013 The Telegraph interview, Keaton talked about Pacino within minutes. The "Something's Gotta Give" star had fallen deeply for the actor while they appeared on "The Godfather" and its sequels.

The reaction [Diane] Keaton had while her ex-boyfriend [Al Pacino] spoke showed how much she still loved and cared for him.

Keaton confessed that she'd been taken with Pacino from the start. She recalled how their relationship had been fantastic in some ways but explained what the actor hadn't been to her, stating:

"He wasn’t the love 'of my life'… He was the love of that time of my life. Each man had a different decade."

AL AND DIANE NEVER MARRIED

Diane Keaton projected on a video screen while Al Pacino speaks onstage during the American Film Institute's 45th Life Achievement Award Gala on June 8, 2017, in Hollywood, California. | Source: Kevin Winter/Getty Images

Neither the Oscar Award-winning actress nor Pacino married later in life. Keaton explained how she wasn't saddened by not having married because she felt she needed "a maternal aspect," adding:

“I don’t think it would have been a good idea for me to have married, and I’m really glad I didn’t, and I’m sure they’re happy about it, too.”

Duke, Diane, and Dexter Keaton at the afterparty for American Film Institute's 45th Life Achievement Award Gala Tribute to the actress on June 8, 2017, in Hollywood, California. | Source: Emma McIntyre/Getty Images

The star thought she lacked the "nurturing" quality a husband would've required. However, she did become a single parent by adopting two children, a daughter, Dexter, adopted in 1996, and a son, Duke, adopted in 2001.

Even though he also never married, Pacino did welcome three children. His offspring came from two different girlfriends; with Jan Tarrant, he had his first child, Julie, then with Beverly D'Angelo; he has twins, a daughter, Olivia Rose, and a son, Anton James.

Pacino also dated Lucila Polak, and her daughter, Camila Morrone, refers to him as her stepfather, although the former couple never married. Pacino's 2017 AFI speech indicated that he and Keaton left things on good terms.

He greeted her at the ceremony by mentioning how he liked her black hat. In his tribute to her, where he mostly spoke about Keaton, he ended his speech by saying:

“You are an artist. You’re a great artist, Diane. I remember it, and I love it. I love you forever.”

Keaton's reaction while her ex-boyfriend spoke showed how much she still loved and cared for him. She appeared pretty emotional despite how things ended between them, and that's a beautiful thing to experience.

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