Scott Disick hasn't been feeling the love from Kourtney Kardashian, his longtime girlfriend and the mother of his two children. In the March 3 episode of Kourtney & Kim Take Miami, Kim Kardashian warns her older sister that if she doesn't show Disick more affection, the notorious party boy may stray.

After failing to find Disick in their new home, Kourtney asks her sister, "Do you know where Scott is?"

"He took the boat out," the 32-year-old replies while lounging on her bed and surfing the internet. "I think he's just kinda trying to, like, do his own thing. . . He just feels like you only care about the kids."

Kourtney, 33, argues that Mason and Penelope "are my first priority," and implies that Disick shouldn't take that personally. "You don't want even alone time with Scott," Kim counters. "It's weird."

"For me, I like doing stuff all together as a family," Kourtney responds.

Standing up for Disick, Kim says, "I mean, you can't neglect him. He was such a big part of your life before you even had [kids], so now that they came along, you're going to ditch Scott? You need to give him a little bit of attention."

Kourtney insists she's "not ditching" her boyfriend, but Kim sees it differently. "He's gonna cheat on you and it'll be your fault. . . You just don't put in any effort. You're going to lose him. No joke. You're literally going to end up, like, alone."

In a confessional, Kourtney takes her sister's warning more seriously. "Just hearing Kim say those words really just freaks me out," she says. "Not that Scott would ever cheat on me, but I just really don't want this for my relationship."

Kourtney & Kim Take Miami airs Sundays at 9 p.m. EST on the E! network.