The 25-year-old model and television personality discussed Kylie Jenner's pregnancy and being a "cool aunt" to her nieces and nephews during Tuesday's episode of The Tonight Show starring Jimmy Fallon.
On The Tonight Show, Jenner recalled how Kylie Jenner announced her pregnancy.
"She called me, and I answered the phone, and she just had her little sonogram -- like, a picture of her sonogram. And I was like, 'Oh, my god,'" Jenner said.
"I wasn't really shocked 'cause I, like, felt like it could happen someday soon, but I was excited," she added. "I was very excited, and -- It's just a blessing. It's amazing."
Jenner said she is "alright" at babysitting her many nieces and nephews, who also include Kourtney Kardashian's three kids, Mason, Penelope and Reign, Kim Kardashian's four kids, North, Saint, Chicago and Psalm, and Khloe Kardashian's daughter, True.
"I always want to be, like, the cool aunt and, like, liked, I guess, by all of them," Jenner said.
"There is 18 of them now, going on 20. There's two on the way," she added, confirming her brother Burt is expecting his third child with his girlfriend, Valerie Pitalo. "It's fun. It's really fun. I try and be chill."
Jenner said her boyfriend, professional basketball player Devin Booker, "loves" her nieces and nephews as well.
"Him and Stormi have an amazing relationship," she said. "She has the biggest crush on him, and I'm, like, jealous sometimes."
On The Tonight Show, Jenner also played a game where host Jimmy Fallon read quotes from Jenner's mom, Kris Jenner, and sisters and had Jenner guess which person said it.
Jenner attended the Met Gala Sunday with Kim Kardashian and Kris Jenner.