United Kingdom, Oct. 18 -- Kaia Gerber is "down on [her] knees" with grief for her late brother Presley Gerber.

The 25-year-old model paid a heartfelt tribute to her sibling after he passed away at the age of 27 on 20 September, in which she remembered him as her "ultimate teacher" and the "love of [her] life" as she expressed her regret that he had passed away "first" after she had spent so many years following in his footsteps.

Alongside a throwback photo and a video of them dancing as children, Kaia wrote in a series of slides on Instagram: "Prez, I don't have the words, and maybe the tiny mercy is that we didn't need them all along. Words fail and words subtract and words summarize and words always lack truth. And how naive of me to...