Khloé Kardashian Feared Brother Rob Was Her Son Tatum's Sperm Donor: 'That Would Not Surprise Me'

Khloé Kardashian's son's uncanny resemblance to her brother Rob Kardashian may have had her questioning Tatum's paternity.

During an interview on the "SHE MD" podcast Tuesday, the "Kardashians" star -- who shares Tatum, 21 months, and daughter True, 6, with ex Tristan Thompson -- admitted to making the NBA player take three paternity tests for their son, who was born via surrogate.

"He was so offended," Khloé told hosts Dr. Thais Aliabadi and Mary Alice Haney of her ex.

The Good American founder explained that she wanted DNA proof that Thompson is Tatum's dad because she thought their son "doesn't look like" either of them.

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Khloé quipped that she even suspected that Rob's sperm may have been used accidentally instead of Thompson's due to how closely her son resembles his uncle.

"My son looks just like my brother," she said. "Because he was an IVF baby or a surrogate baby, I was like, 'Rob, have you ever donated sperm somewhere?'"

With a laugh, Khloé added, "In this family, that would not surprise me, but that would be so disgusting. But I remember she [her doctor] was like, 'You've already done a DNA test!' I go, 'I need to do another one, I need to figure it out.'"

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The reality star shared that Tatum also took after her late father, Robert Kardashian, when it comes to looks and personality.

"My son's a year-and-a-half, and he's sarcastic, and my dad had a really dry, silly, just crazy sense of humor, and there's glimmers of my dad in Tatum, and I'm like this is so freaking weird, but it's just how God works, and I love it," she explained.

This is not the first time Khloé has commented on how much her son Tatum resembles her brother Rob.

Last month, she posted via Instagram Stories an adorable photo of True and Tatum, calling them "my mini Me and my mini Robert" in the caption.

In December last year, Khloé called her son "Baby Rob" as she uploaded photos of her youngest child making cute faces for the camera.

"He knows what he's doing with that face," she captioned the Instagram post, adding the hashtag, "#BabyRob."

Kardashian fans have also noticed how much Tatum looks like Rob.

In the comments section of a February Instagram post featuring Khloé and Tatum, fans could not help but gush over the resemblance.

"He has your dad and Rob's whole face," one comment read, while another person wrote that Tatum looked like "Rob's twin."