A source told E! News the two have experienced a series of "ups and downs" since returning from their romantic getaway to Italy.
"Kourtney and Younes have been arguing since coming back from their big Italy trip and have truly not been getting along," the insider told E! News.
The source said the two "decided to take time apart but ultimately it led to a split." Younes was also recently photographed getting cozy with Jordan Ozuna in Mexico.
"Kourtney is upset but she is trying to focus her energy on other things and stay busy," the source continued. "Kourtney doesn't plan on calling attention to it publicly and wants everything to blow over. It's upsetting to her. They have been having ups and downs for the past month. There was a huge chance they were going to get back together and they were working on things. But now that these photos surfaced, things are definitely over."