Speaking to Digital Spy, the former Olympian explained that he is "not worried" about the girls - aged 16 and 14 respectively - being in the public eye.
"I've been in the public eye since the [Olympic] Games 36 years ago," he said. "I know the game, I know how it's played.
"I watch these little girls like a hawk. I talk to them all the time about keeping this proper perspective. You've got to look at this as a business, and it can be a very good business and you can build a very nice career here, but you have to keep it in proper perspective about what's going on and I watch them very closely."
Bruce, who pointed out that the pair "literally grew up on the show", added: "They have been great kids, good people, how they treat other people, the way they've dealt with it - I've been very impressed with them, because it's not easy.
"[They] literally have grown up in front of the cameras and become very successful young women, and I'm very proud of them."
Kylie, who recently appeared on the cover of Seventeen with Kendall, has denied rumors that she is dating Australian popstar Cody Simpson.
> Read our full interview with Bruce Jenner