The expansive and frequently dishy interview therein included revelations about her father, Caitlyn Jenner, formerly Bruce.
Before the public transition, Kendall confided, she and Kylie once 'thought he was cheating on my mom, because he had makeup and nail polish. One time we found those squishy boob things. We found wigs. And then one time I actually ran into her. In this house. She had no idea.'
Kris Jenner's penultimate daughter explained: 'She would wake up really early just so she could dress up and move around the house and get that little kick for the morning, and then go back to being Bruce—take us to school, totally normal.'
In a particularly jarring stroke, Kendall said: 'My mom knew. She knew since their third date.' At which point, Kris Jenner burst into the room with brownies.
source
I put Bruce in the title this was before she was Caitlyn she caught her dad dressing up before she came out and said she wanted to be a woman and wanted to be called Caitlyn. Interesting and I'm sure Kris knew there's no way she didn't know about this so I believe what Kendall said.