Kendall Jenner, 14, and Kylie, 12, are Kourtney, Kim and Khloe's half-sisters.
"All I can say is wow!" Kourtney writes. "I just received Kendall's final shots from a shoot she did last week with one of our favorite photographers, Nick Saglimbeni, and I am speechless. She looks amazing!! So proud of you, Kendall."