Kim Kardashian celebrated Kylie Jenner's birthday by sharing throwback pics of her little sister on her website — and they are priceless!

While the now 19-year-old is unrecognizable in the selfies, there is no denying the bond these two sisters share despite their nearly two decade age gap.

"Even though you are the youngest among us, I am constantly amazed by your maturity," Kim wrote to her look-alike sibling. "I am always learning from you and inspired by your dedication to your business. You are so true to yourself and I love that!"

Click through the slideshow for more classic sister selfies!