Alexa Ray Joel Taught Sister Sailor to Deal with Critics After Her Own 'Painfully Shy' Teen Years

That's what big sisters are for!

Christie Brinkley's two daughters, Alexa Ray Joel and Sailor Brinkley Cook, may be making waves with their sexy Sports Illustrated Swimsuit family photo shoot, but both ladies have previously dealt with body image issues and criticism while growing up in the public eye. After all, they have famous parents — sharing a supermodel mother while Alexa's father is legendary singer Billy Joel and Sailor's father is architect Peter Cook.

Alexa is a singer-songwriter like her dad, and although she loves the stage now she wasn't always a fan of the attention that comes from a life in the spotlight. The 31-year-old says she and Sailor, 18, have swapped stories about dealing with constant media attention — and oftentimes harsh criticism — while growing up.

"I was a painfully shy teenager, " Alexa admits. "Before I decided to be a performer, I was a little shell-shocked when paparazzi would be around. When you're young, it's easy to pick on you. There was a tabloid page that would draw things on my face. When you come from privilege, they just see you as, 'Oh, she got it all handed to her.' "

RELATED VIDEO: Christie Brinkley's Daughter Sailor Reveals How Hard It Is to Follow in Her Mom's Supermodel Footsteps

RELATED PHOTOS: Christie Brinkley's Most Iconic Sports Illustrated Swimsuit Photos

Fabio Chizzola

Alexa says that she's "very impressed" with her younger half-sister, who has a contract with IMG Models.

"She came into her own certainly sooner than I did!" Alexa shares.

• For more on Brinkley, her gorgeous daughters and their life with a supermodel mom, read this week's issue of PEOPLE, out on newsstands Wednesday.

The sisters both wrote lengthy essays on their Instagram accounts encouraging other girls to love themselves and their bodies after the Sports Illustrated image of them with their supermodel mom hit the web.

Sailor wrote, "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 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."

Emmanuelle Hauguel/SI

Alexa had similar thoughts to share, writing, "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."

Dying to see the whole issue? The magazine hits newsstands Feb. 15.