Jessica Simpson Celebrates Nephew Bronx's 14th Birthday with Sweet Photo: 'You Are a Gift'

Jessica Simpson/instagram

Jessica Simpson is paying tribute to her nephew Bronx on his birthday.

On Sunday, the fashion designer, 42, shared a sweet post on Instagram in honor of sister Ashlee Simpson Ross's son turning 14. In the snap, Simpson poses with Bronx, whom Simpson Ross shares with ex-husband Pete Wentz, as the pair smile in front of a frosted cookie cake.

"Happy 14th Birthday BX!!! I love you SO very much. You are a gift to everyone who is lucky enough know you, love you and be loved by you," Simpson wrote. "Being your Aunt…has been…WILL ALWAYS BE…one of the most precious blessings of my life! Thank you for being YOU! 💚🎉💫"

Simpson also praised younger sister Simpson Ross, 38, in the caption for being her "role model."

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RELATED: Ashlee Simpson Ross Shares Family Photo with All 3 Kids in Honor of Son Ziggy's 2nd Birthday

Along with Bronx, Simpson Ross shares daughter Jagger, 7, and son Ziggy Blue, 2, with husband Evan Ross.

The "With You" singer is mom to daughters Maxwell Drew, 10, Birdie Mae, 3, and son Ace Knute, 9, with husband Eric Johnson.

Last week, Simpson enjoyed a special generational moment with her mom and her daughter. The fashion designer posed on a homey, winter-like set to promote her Jessica Simpson Collection holiday line, posing with her mom Tina Simpson, as well as daughter Maxwell.

Tina and Maxwell showed off their matching fuzzy slippers, with the pre-teen making a puckered face as she leaned into her mom in the sweet photo.

"Three Generations of Cozy! Thanks for having us @hsn!" the mom of three captioned the photo.

Simpson has previously celebrated daughter Maxwell's style, saying she has a "fashion-forward sensibility."

"Maxwell was born with a fashion-forward sensibility and a keen eye for creating her own style, but notices others' authenticity and celebrates it," Simpson previously told PEOPLE. "She has always known what she likes and remains very confident and vocal about her choices."