Tatum Thompson, their surrogate-born son, acts like her late father and looks like brother Rob Kardashian, so Khloé Kardashian ordered his father, Tristan Thompson, do three paternity tests.
The reality TV star told the SHE MD podcast that she forced Thompson do repeated paternity tests after realizing their one-year-old kid didn't look like her and Tristan.
The video above shows her asking Dr. Thais Aliabadi and Mary Alice Haney, “Because he was an IVF baby or surrogate baby, ‘Rob, have you ever donated sperm somewhere?” I had Tristan perform three Tatum DNA tests. He was offended, and I said, ‘He doesn’t look like me.’”
She remarked, “‘He could have been my brother's by accident!'”
“In this family, that would be expected but disgusting. I recall my doctor saying, ‘You've already done a DNA test!’ ‘I need to do another one, I need to sort it out,’” Kardashian said. 
My one-and-a-half-year-old kid is snarky. Tatum has hints of my dad's dry, funny, insane sense of humor, and I'm like, ‘This is so freaking weird.’ God works that way, and I adore it.”
Kardashian said Thompson's adultery during surrogacy made it hard for her to bond with the kid.
Khloé called Tristan a “incredible father” to Tatum and True, their six-year-old daughter, on the show.
“He made mistakes, but he's now the nicest guy, and we get along well,” she added.
“We weren't meant to be together, but he was meant to father these kids. My parents got along well, so I'm pleased we do too.”