Scott Disick and Sofia Richie Break Up: He 'Thinks She Might Change Her Mind,' Says Source

Scott Disick and Sofia Richie are over, PEOPLE confirms.

According to a source, Richie, 19, ended the relationship with Disick, 35.

“Sofia broke up with Scott,” the insider tells PEOPLE, adding that Disick’s “old issues” contributed to the split.

“When Scott drinks, he is a sloppy mess and fools around,” the source says.

As for how Disick is dealing with the break up, “Scott seems fine,” the insider tells PEOPLE. “He even thinks she might change her mind. He isn’t really taking it seriously.”

The news comes amid heightened speculation about their relationship status after Disick was spotted looking flirty with a mystery woman at Kanye West‘s Ye listening party in Jackson Hole, Wyoming, on Thursday night. Disick reportedly told guests that he and Richie were no longer together, according to TMZ.

Richie and Disick — who shares three kids with ex Kourtney Kardashian — first sparked romance speculation in May after they were pictured cuddling up aboard a yacht in the south of France during the Cannes Film Festival. At the time, Richie — who previously dated Justin Bieber — adamantly denied anything romantic was going on, tweeting that the two were “just homies.”

Months later, the two had become “inseparable,” a source told PEOPLE in mid-September. They confirmed their romance shortly afterwards with friends in Miami, capping off the trip with a few PDA-packed days in Mexico.

In the months that followed, the couple spent much of their time traveling together, enjoying a romantic Italian getaway and another trip to Mexico. They also spent time together stateside and were regularly spotted in Los Angeles and New York City.

While a source previously told PEOPLE that Richie’s famous father Lionel wasn’t too pleased about the relationship — “Lionel knows Scott’s playboy ways, and he doesn’t want to see his daughter get hurt,” the insider said — the model had insisted that her dad was on board.

“He’s good — he’s been very nice,” she told E! News at the SAG-AFTRA Foundation Patron of the Artists Awards in Beverly Hills in November.

“He’s been very cool,” she added. “He’s very supportive, whatever that means,” she added as Lionel, 68, jokingly pointed a gun-shaped hand gesture at his head.

“I am into her business, and she’s trying to keep me out of her business,” he said.

Throughout their relationship, Disick and Richie’s went through ups and downs. A source told PEOPLE in early November that it was “starting to fizzle.”

“They’re starting to argue more, and it’s bothering Sofia,” said the source. “She thought he would be more serious about their relationship and is finding herself to be more frustrated with him as time goes on. Everything everyone has been telling her to look out for, she’s now starting to see for herself. It’s really upsetting for her, but she is trying to work through it.”

But just weeks later, another source told PEOPLE the two were “very serious” and that Richie has been a positive influence on Disick, who is known for his late nights out and has openly struggled with alcohol abuse.

“She’s been great for him,” the source said. “She’s made a big impact on his life and hasn’t partied at all since they met.”

“His friends adore her and nobody notices the age difference,” added the source. “She is very mature, she grew up in Hollywood and has always been in older situations. They seem really happy.”