How 'Huge Age Difference' Led to Jennifer Lawrence's Breakup with Darren Aronofsky

"They were never destined for marriage," a source tells PEOPLE of Jennifer Lawrence and Darren Aronofsky in this week's issues

Jennifer Lawrence and director Darren Aronofsky got together while filming mother!, but two months after the movie’s September release, the couple of one year broke up.

“Once they are onto new projects and interests, it’s harder to keep up relationships of any kind,” a show business source tells PEOPLE in this week’s issue. “They were never destined for marriage. They had fun, shared many beliefs, and enjoyed what they could learn from each other.”

A source close to the pair suggests the age difference between the Oscar winner, 26, and the producer-director, 48, played a key role in the split.

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“There is a huge age difference, and they are different people,” the insider says. “Each has to look practically to the future. Jen has yet to figure out her life and how it will evolve. He has responsibilities in life that she has yet to experience.”

Since getting together in September 2016, Lawrence and Aronofsky kept their relationship private, only making their public debut as a couple at the Venice Film Festival photocall nearly one year later. Less than two weeks before PEOPLE confirmed their split, they were seen cozying up at the 2017 Governors Ball.

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“Each was infatuated with the other. She was attracted to his brilliance and education, and he was in awe of her talent and personality,” the source adds. “They have amazing respect for each other given the huge age gap, but other things were not on the same level.”

The pal continues, “Although they are both kind of kooky and unusual, he is quieter while she speaks from the hip and loves to astonish.”

Next, Lawrence will appear in Red Sparrow and 2018’s X-Men: Dark Phoenix, while Aronofsky has multiple production projects planned for 2018, along with a directing gig on the documentary One Strange Rock.

“They are both workhorses but personally different,” the source says. “It was fun while it lasted.”