Scott Disick and Kourtney Kardashian
Scott Disick blames ex Kourtney Kardashian for not receiving an invitation to Khloe Kardashian's birthday. Pictured: Kourtney and Disick attend the launch of AG Adriano Goldschmied's 'backstAGe presents:' initiative featuring The Black Keys at the Marquee Nightclub at the Cosmopolitan of Las Vegas Feb. 14, 2011 in Las Vegas. Getty Images/Ethan Miller

Scott Disick considers himself a member of the Kardashian family, so he is understandably upset that he is not invited to Khloe Kardashian's birthday.

In a preview for this Sunday's "Keeping Up with the Kardashians" episode, Scott expresses his disappointment to the mother of his three children over not receiving an invitation to Khloe's birthday. "I didn't even get invited to her birthday. And I'm family," he tells Kourtney and Kim Kardashian (as quoted by People).

"That was really sweet. That made me feel really good," he says sarcastically.

Scott then says that he doesn't blame the birthday girl, but his ex. "There's only one person that would have gotten me not invited and that's Kourtney," Disick adds. "I highly doubt that Khloe was like, 'The last person I'd want at my surprise party would be Scott.'"

Scott and Kourtney have a confrontation over Khloe's surprise birthday bash. According to Scott, he understands if his ex does not invite him to her own birthday, but not if she prevents him from going to her sister Khloe's because he considers them his family too. He wants to be there for Khloe on her special day.

At first, Kourtney says that she just doesn't want paparazzi seeing him coming to the venue, but later on, she admits that she simply doesn't want her ex in the party. It seems Scott is right after all.

"I was trying to be positive. I didn't want to say I just didn't want you there. So if I can't say anything nice, I just won't say anything at all," Kourtney explains.

Despite Kourtney and Scott's rocky relationship after their split, they could not just cut ties because they share three children together: Mason, 7, Penelope, 5, and Reign, 2. In the previous episode of "KUWTK," Disick confessed that he wanted a fourth child with Kourtney. However, the latter is reluctant to give in because of his attitude.

Disick also revealed that he has a hard time finding happiness after his split from Kourtney. "Looking at my perspective, [Kourtney] was on vacation with one man the whole trip — that looks like a happier scenario than me jumping around, trying to find happiness and these girls are not fulfilling that. I'm just not happy with anybody," Disick said.

Disick is currently in a relationship with Sofia Richie. Meanwhile, Kourtney is seeing Younes Bendjima.