Los Angeles, California - Kourtney Kardashian has fired back at negative comments about her physical appearance under a photo shared by younger sister Kim.

The newly-45-year-old was seen rocking a black bikini alongside Kim and Khloé Kardashian in a sweet birthday tribute shared by the SKIMs mogul.

"Happy Birthday Queen @kourtneykardash," Kim wrote on Thursday. "There's no one on this planet that I have spent more time with and have all of the same memories with growing up than you and I cherish them all

Unfortunately, one user put a damper on the celebratory post by writing, "Now you know she's not going to like this photo… lol it's her bday Kim" in a since-deleted comment, per PEOPLE.

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Kourt was quick to defend herself and send an important message of self-love to other women – especially new moms like herself.

"I LOVE this photo! It is me and my sisters having the best time on a trip with our kids... and the memories to last forever!" the reality star wrote. "And I LOVE this body that gave me my 3 big babies and my little baby boy."

The mom-of-four welcomed her youngest, Rocky Thirteen Barker, last November, and she has been quite candid about the realities of post-partum life via social media.

In another post from the Turks and Caicos vacay where Kim's snap was taken, Kourtney shared a photo of herself smiling as she swam in the clear blue waters.

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She then reshared the image to her Instagram story with more words of wisdom for her fellow moms.

"The pressure put on us to bounce back when everything is new and different isn't realistic," she said. "Life is beautiful, you are beautiful. Just a little reminder (for me too;)."

Along with sweet messages from her sisters, Kourt received a heartwarming tribute from her husband, Travis Barker, who dropped several never-before-seen photos of The Kardashians star.