The supermodel makes a major return to the magazine after 13 years, accompanied by her 31-year-old and 18-year-old daughters

Christie Brinkley, 63, Is Back in Her Bikini for Sports Illustrated – with Her Daughters!

Image zoom Emmanuelle Hauguel/SI

Brinkley is joined by her daughters, Alexa Ray Joel, 31, and Sailor Brinkley Cook, 18, in the magazine, on newsstands Feb. 15, and she says their encouragement was key to getting her back in her bikinis.

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“My first thought was, ‘At my age? No way!'” she tells PEOPLE exclusively in this week’s issue. “When I turned 30, I was like, ‘This is the last time I’m posing in a bathing suit!’ When this issue comes out, I’ll be 63. I thought, ‘Those days are over.’ But to get to do it with my girls, I thought, ‘One last go!'”

In the sexy spread, the trio wears coordinating black swimsuits, including a cutout mesh one-piece on Brinkley, as they stand on the shoreline of an idyllic Turks & Caicos beach. Brinkley also poses solo in a number of skimpy two-pieces, including the show-stopping red bikini below.

Image zoom Emmanuelle Hauguel/SPORTS ILLUSTRATED

Sailor, Brinkley’s younger daughter with ex-husband Peter Cook, who has already dipped her toe into the modeling world, says the SI Swim experience was “very empowering and liberating.”

Alexa, however, had a different reaction when asked to participate in the shoot and “needed to be talked into embracing new experiences.”

And even though Brinkley admits to battling her own insecurities, she hopes her bikini-clad return will spark a conversation on ageism in the industry. “In a country that’s very ageist, people love to put you in little boxes,” she says. “Women feel very limited by their numbers. On a personal level, I thought, if I can pull this off, I think it will help redefine those numbers and remove some of the fear of aging.”

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.