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The 24-year-old posted an adorable throwback of her cradling her baby sister at the beach. In her hilarious caption, she thanked their mother, Yolanda Hadid, for birthing Bella.
"INTL. @bellahadid DAY," she said. "MY VERY OWN CUSTOM CABBAGE PATCH KID I RAISED RIGHT FROM THE SEEDLING ! THNX @yolanda.hadid !"
And the celebrations didn't stop there! Chanel's Paris Fashion Week savior posted even more throwback photos of her and baby Bella to her Instagram story.
"Don't look at or touch my custom bestie ever again," Gigi quipped on a photo from the day her model sister was born.
Another shot from Yolanda's hospital room shows the mother helping a baby Gigi hold Bella, presumably for the first time. Gigi's last post honoring her sister shows the two as kids, dressed in pastel dresses with floral headbands. It's so very '90s.