"My Heart Dropped" first time i saw Caitlyn Dressed as Woman - Kendall Jenner

Kendall Jenner had hints about Caitlyn’s transition before she announced it to her family.

The 21-year-old reality star said she and her sisters found clues around the house growing up: a wig, nail polish. A year before her father came out, Jenner even saw her dressed as Caitlyn during a middle-of-the-night kitchen run.

 "My heart dropped," she told Harper’s Bazaar. "That's when she would dress as herself, at four in the morning, before we would get up. So that was like, 'Whoa,' for a second."

By the time the 67-year-old former Olympian came out as transgender in April 2015 on the cover of Vanity Fair, her family already “kind of knew.”

"When she told us, and told us that it was going to be a real thing, it was an emotional couple of months,” Jenner told Harper’s Bazaar.

“And if I would talk about it, I would cry, just because you're mourning someone … losing someone. The person is still there, of course, but physically you're losing someone. It was my dad who I grew up with my whole life and who raised me. It's an adjustment, for sure. But honestly, you start to realize that this person is still alive. This person is still here. They are still a blessing. They are still awesome. I realized that I should just be thankful that I still have my dad. It starts to just become normal. You're just like, 'OK, cool.’"

In her upcoming memoir, “The Secrets of My Life,” Caitlyn Jenner confirms that she underwent a gender reassignment surgery in January.

“I just want to have all the right parts. I am also tired of tucking the d--n thing in all the time,” she wrote.

“I am going to live authentically for the first time in my life ... I am going to have an enthusiasm for life that I have not had in 39 years since the Olympics, almost two thirds of my life.”