Rob Kardashian to his siblings: You’re not skinny!

The entire Kardashian family, including siblings Kourtney, Kim, Khloe, and Rob, sit down with Oprah Winfrey for "Oprah's Next Chapter" on Sunday during which Oprah will try to get to the bottom of why the "Keeping Up With the Kardashians" klan is such a cultural phenomenon. In the interview, a clip of which you can see above, Winfrey asks if they would have found such fame if they weren't attractive, a question Rob was eager to answer — whether or not his sisters wanted him to.

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"They're not skinny women," Rob, 25, quickly replied. "They're not models here." When his sisters ribbed him for his response, he added: "I'm just saying: You're great role models for women, young girls."

Kim, 31, tried to offer more insight. "I don't think [our success] would have happened if we were all skinny, pretty models. I think it had to do with the curves, the dark hair. I remember when the wave of Jennifer Lopez and Salma Hayek and these beautiful Hispanic women came into light. I looked up to them and I loved them but I thought: Where are all the Middle Eastern women?" said Kim, whose family is of Armenian descent. "We took that category or helped broaden that. In life, I think people just have 'it' — I can't explain what 'it' is."

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Winfrey, who she had never met the Kardashians prior to the interview or watched any of their E! shows, said she wanted to sit down with them to figure out why they had become so popular. "Why do so many people love to watch their every move and why do so many others love to hate them," Winfrey wrote on Facebook. "Are they completely ego centered? Are they really 'famous for being famous' or is there something more?" Noting that by the end of the interviews, during which she also grilled Kim about her 72-day marriage, she said: "I 'GOT IT.'" Winfrey also said Scott Disick, Lamar Odom, Khloe, and Kim were the ones who surprised her the most.

To watch the full interview, tune into "Oprah’s Next Chapter: Kardashian Family" this Sunday at 8 p.m. ET/9 p.m. PT on OWN.