Scott Disick didn't think Kourtney Kardashian would "become so serious" with her boyfriend, Younes Bendjima.
The Keeping Up With the Kardashians star first met the former boxer in October 2016 and they've been spending time together ever since. Over a year later, the couple is still going strong and Kourtney's ex isn't too pleased about it, according to a source.
"Scott is still insanely jealous of Younes," the insider tells E! News. "He just can't come to terms with the fact that Kourtney has found true happiness with someone else."
And even though Scott has been dating Sofia Richie for months now and is "happy" with her, he "can't deal with someone else having Kourtney."
"It makes things between them tense and unpredictable," the source adds. "Kourtney never knows when he is going to fly off the handle or go nuts about something. Scott just never thought it would last this long with Younes or become so serious. Nobody really did."
But Kourtney is "very happy" and "in love" with Younes, the insider shares, adding, "Scott is hurt she chose someone else and it really bothers him. He can't control his emotions about it and lets it all out."
Kourtney and Scott, who have three kids together, called it quits in July 2015 after nine years together. Younes is Kourtney's first serious relationship since her split with Scott.
One insider told us in May 2017, "Scott doesn't like Kourtney dating Younes at all. He doesn't want to see photos of them or know about it. Kourtney has tried to give Scott a heads up that he might be seeing photos, but Scott can't stand seeing her with someone else, especially Younes."
On a November 2017 episode of Keeping Up With the Kardashians, Kourtney told Khloe Kardashian the story of how she met Younes the night before Kim Kardashian's terrifying robbery in Paris.
"Yeah, we like walked into a bar and Stephanie [Sheppard] was across from me and she kept going, 'This guy's cute over here,'" Kourtney recalled. "He was friends with our friends. He would walk in, say hi, shake hands with like our security or whatever, but like not say hi to us. And then I was like, 'Why do you hate us?' I was just drunk. Once I said that he literally like grabbed my hand and was like, 'It's five in the morning. We're leaving. And the next night Younes was like, 'Bring your ass here.'"
Kourtney went on to tell Khloe, "When we walked into that club was when we went to the bathroom and got the phone call about Kim. So then the party was over. And then he was like, 'I'm not leaving you guys,' and he like had to translate everything."