By Meghan Overdeep
Updated Oct 22, 2015 @ 8:45 am
Kim and Kourtney Kardashian
Credit: Gregg DeGuire/WireImage

Big sister Kourtney Kardashian, 36, wished Kim Kardashian a happy 35th birthday in the sweetest way. Kourtney shared a throwback photo of the two of them via her Instagram account along with a heartfelt message for her superstar sibling.

"She has been my partner for life. We always seem to end up on the craziest adventures together," the reality star captioned the photo from their teenage years. "I love and admire the person you have become and learn from you every day. Happy Birthday!"

The photo shows the two Kardashian sisters before they were famous as fresh-faced teens, wearing sweatshirts and making matching hand signs.

For her 35th birthday, Kim took the opportunity to share 35 life lessons she's learned on her website, From tips on beauty and fashion to family, self-confidence and gratitude, Kim has picked up plenty of wisdom throughout the years, but perhaps the most telling piece of advice she offers is number one on the list, literally.

"1. Family first. Always."