This story was written by Emily Kirkpatrick and originally appeared on People.com

On Monday, Christie Brinkley and her two daughters, Alexa Ray Joel and Sailor Brinkley Cook, proved that the supermodel genes run strong in this family, posing for Sports Illustrated’s forthcoming swimsuit edition. But just because they’ve inherited their mom’s iconic bone structure doesn’t mean these young ladies have always felt confident enough to pose in a two-piece for a major magazine. After the initial image of them with their supermodel mom was released, both Joel and Cook wrote lengthy essays on their Instagram accounts encouraging other girls to love themselves and their bodies.​

I've had issues with my body image since before I can even remember. I grew up not loving how I looked and felt held back because of it. I don't know why I always felt that way, sure I had baby fat and definitely went through a plethora of awkward phases, but I had a family that loved me i had friends who made me laugh etc. But for some reason I still looked in the mirror and always somehow found something to pick on. I went from being "too fat" to "too thin" to "too muscular" and I never felt satisfied. My body and I have been through it all. But recently I have been liberated. I am healthy, i treat myself well, and for that i'm happy. I've looked in the mirror and been able to LOVE the things about my body that beauty norms deem 'undesirable'. I now have grown to know that my body is worthy of so many great things. I don't need to be a size 0 to believe in myself. My body carries me each and every day, it loves the people i love, it holds what makes me healthy and strong, it bends it shakes it runs and it CHANGES. That is okay and that is beautiful. I could not be more grateful to the beautiful and strong @mj_day for including me in this years Sports Illustrated Swimsuit Issue 😭😩❤ This is more than a magazine to me and always has been. As a growing young woman SI showed me all bodies are different and all bodies are worthy of celebrating. Thank you thank you @si_swimsuit for celebrating my beautiful mama, my beautiful sister, I, and ALL WOMEN!! How lucky am i?! 😩😍😍 i think I'm dreaming. 😭😩😩 thank you!!!!!!! ❤ (Also, thank you @hayleythorpeholla and @v_beast and everyone at @dogpound for changing my life 😭❤) More to come!!!!!!!!

A photo posted by Sailor Brinkley Cook (@sailorbrinkleycook) on

Her half-sister Alexa Ray Joel, 31, had similar thoughts to share, writing (over the course of a few Instagrams from the shoot), “Let’s STOP degrading and START celebrating ourselves and others, from both the inside AND out. There's far too much degradation, competition, insecurity, and unhealthy standards associated with women and their bodies- particularly on social-media … We are all perfect, just as we are. Please know that. Thank you @si_swimsuit for showcasing all heights, shapes, and sizes. For within our distinctions, our quirks, and our self-perceived ‘flaws’… therein lies the beauty.”

In a second post she added, “This was a lesson in learning to let go, take the plunge, and embrace myself from both the inside AND out- which is something I struggle with each and every day. My purpose is to now pass along this lesson of unconditional self-love and self-respect to every woman who’s willing to listen.”

And mom Christie weighed in on her own insecurities during the shoot, writing on her Instagram, “Thank you Sports Illustrated for sending the powerful message that good things come in packages of every size and do not come with an expiration date!” (She also added the cheeky note, “My kids think I walk on water, so let’s not mention the apple box concealed just under the surface.”)