Kourtney Kardashian paid tribute to sister Kim Kardashian on her 45th birthday. Taking to Instagram on Tuesday, October 21, to share a carousel of throwback photos that captured Kim through the years, Kourtney, 46, captioned the post, "Best friends forever." The older sister kicked off her carousel with a stunning black and white snap of the pair posing back-to-back with matching bobs before launching into a hilarious photo of the duo sporting cosmetics to make them appear old and wrinkled.