The reality star says she first thought her step-parent was just a cross-dresser.
Kim Kardashian took to her new website to share what it was like being one of the first in her family to know about Caitlyn Jenner's identity as a transgender woman.
In a first-person essay, the 34-year-old reality star recalls when she found the former Olympian, who identified as Bruce Jenner at the time, wearing women's clothing.
"My mom was out of town with my little sisters, visiting my grandmother in San Diego, and I was living with her and Bruce at the time in Calabasas," Kim recalls. "I came home from a friend's house and walked into the garage and Bruce was there, dressed up as a woman. Heels, wig, makeup and all! I don't remember specifically what he had on because I put my head down and ran into my bedroom."
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Kim also revealed that her late father, Rob Kardashian Sr., had talked about Caitlyn's desire to dress like a woman. "Had I not overheard my dad and his friends discussing rumors that Bruce would dress up as a woman years before (when I was about 11 years old), I never would have believed what I was seeing," she writes. "I thought my dad was jealous of my mom's new husband, that he was joking with his friends on the phone, but suddenly I knew it was all true."
The Keeping Up With the Kardashians star goes on to admit that she got a little spooked after catching Caitlyn in the garage. She says that "within 30 seconds" she had packed a bag and drove to older her sister Kourtney Kardashian's house to spend the weekend.
WATCH: Kim Kardashian Affectionately Calls Caitlyn Jenner a 'Tomboy'
Kourtney thought her sibling had caught Caitlyn cheating, of which Kim says she responded, "No, I wish."
The girls then started Googling episodes of The Oprah Winfrey Show to try to find an explanation as to what Kim had witnessed. "For over a decade, we assumed he was a cross-dresser, not transgender," Kim writes.
WATCH: Kim Kardashian Calls Out Caitlyn Jenner for Comments About Kris
Thirteen years later, in April of this year, Jenner came out as a transgender woman and has since documented her journey on the reality show, I Am Cait.
She also recently surprised her youngest daughter Kylie Jenner during one of her online makeup tutorials. Check it out:
