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Harper Hammer started off December right! The daughter of Armie and Elizabeth Chambers Hammer turned 3 on Dec. 1.
"Strangers often comment on your beauty, manners and intelligence, but they have no idea of the strength and spirit that lie within," the proud mom wrote in a birthday tribute to her older child (the couple also share son Ford Douglas Armand, 1 in January).
"You are the ultimate gift and we couldn’t possibly love you more," added Chambers Hammer.
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ARROW AND ZEPPELIN ACKLES
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"Happy Birthday to our littlest noodle!" late-night host Jimmy Fallon wrote Dec. 3 in tribute to daughter Frances Cole, sharing an adorable photo of the pigtailed blonde tot flashing a smile at the camera for her 3rd birthday.
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"Today is her day! 5 years ago our family was blessed with a little sunshine that made my heart complete," Bündchen captioned a photograph of herself lifting her daughter up into the air as they enjoyed some time in the water.
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The chef and fiancé Philip Button are also parents to son David, 2½, while Valladolid is also mom to son Fausto, 13.
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She's a teenager! William "Billy" Baldwin and Chynna Phillips' youngest child, daughter Brooke Michelle, turned 13 on Dec. 6.
"A beaming ray of light that cuts through all darkness ... that's you my precious Brooke," the Wilson Phillips singer captioned a photo of Brooke holding a "Happy Birthday" balloon.
"So proud to call you my daughter baby!!!!!" she added. "Happiest of birthday's to you! We all love you so much! #teenqueen"
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Sweet 16! Eva LaRue's mini-me, daughter Kaya, celebrated her milestone birthday Dec. 7.
"I'm proud beyond words of the incredible young woman you're becoming and Love you to infinity and beyond!!" she added. "Happy 16th Birthday my Sweet Pea!!! XoxoMomma ❤️❤️❤️🎉🎉🎉🎂🎁🎈"
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CHARLES "CHARLEY" FELDMAN
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"8 years ago today the sweetest and most loving boy was born!" the supermodel wrote on Dec. 8. "His love for everyone and everything around him is contagious; he melts my heart."
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"You've changed my life in so many ways and I can't believe another year has flown by!" Ludacris wrote on Instagram next to a photo post featuring Cai.
"You always make us all proud in everything you do," he added. "Happy birthday, my little achiever. Continue dreaming big!"
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"You came into our lives in the most 'zen' way, and today you still continue to be our little Yogi baby," the actress captioned an image of one of Zen's twin big brothers (Cy Aridio and Bowie Ezio, 3) giving him a kiss.
"Thank you for choosing us to guide you through your first life years, we are honored," she added.
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SAMUEL "KAI" SCHREIBER
Samuel Kai is 9! Naomi Watts and Liev Schreiber's younger son celebrated his big day Dec. 13.
"Happy birthday 🎈🎊🎂 to my darling Kai. Truly special in every way. My angel❤️ 😇," Watts captioned a wintry photo of her son.
Schreiber shared his own photo of the birthday boy in front of a festively decorated cake, writing, "Happy Birthday Kai!!!"
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Milo William has officially entered his teen years! Dec. 14 marks the 13th birthday of the son of Liv Tyler and ex-husband Royston Langdon.
"My darling milo , My first born is a young man today," Tyler began the caption in a touching post dedicated to her son, sharing a photo gallery of his soccer-themed party and a few snaps throughout his life.
"I am so proud of the person you are. You are the most kind, considerate, compassionate, thoughtful, interesting and funny human person I know," added the actress.
"I am grateful for everyday I share with you and learn so much from you and being your mom," Tyler continued. "I love you more than anything ever!"
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REIGN AND MASON DISICK
From a Monsters Inc.-themed party to a Disneyland trip and even balloon Ferraris, Reign Aston and Mason Dash's Dec. 14 birthday may have been a shared one, but mom Kourtney Kardashian made sure they each felt special — with a little help from aunt Khloé Kardashian.
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"Happy Birthday to our lil' piece of sugar Jasmine Lia," Dwayne "The Rock" Johnson wrote to accompany a joy-filled snap of his daughter, who turned 2 on Dec. 17, reaching out toward her birthday cake,
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Calvin Bradley is only turning 1, but he can already rock a birthday hat like a pro.
"Dearest Calvin, from the second I met you, I knew our lives were changed forever," mom Dylan Dreyer captioned an Instagram photo gallery on Dec. 17.
"Thank you for the absolute joy you've brought into our lives this past year," she continued. "Happy 1st Birthday!! Our hearts are yours forever and ever!"
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DELTA BELL SHEPARD
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"HE IS 2🎉🎉🎉going on 22 of course 🤣," Zee wrote to accompany a photo of Adrian looking quite dapper.
"I'm so in love with my little boy and can't wait to celebrate with him," she raved.
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"Happiest early birthday to my sweetest most loving angel boy," Rachel Zoe captioned a photo of herself with birthday boy Kaius Jagger (who turned 4 on Dec. 22), husband Rodger Berman and their older son Skyler Morrison, 6½.
"May all of your dreams and wishes come true. You have the kindest soul, an enormous heart and a smile that never ends," she added. "You bring happiness everywhere you go to anyone you meet. I love you beyond any words to infinity 💙"
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It seems like just yesterday Phoenix Robert was born, but Nick and Vanessa Lachey's youngest child already celebrated his 1st birthday on Christmas Eve.
"One year ago today this little miracle came barreling into my life and everyday since then has been better for it!" Nick captioned a photo of Phoenix with his birthday cake, surrounded by big sister Brooklyn Elisabeth, 3 next month, and big brother Camden John, 5.
"Happy Birthday little stud!" added the 98 Degrees frontman.
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Christy Carlson Romano and husband Brendan Rooney's baby girl Isabella Victoria also turned 1 on Christmas Eve.
"You are the most amazing, creative, beautiful soul that @thebrendanrooney and I have ever met!" Carlson Romano wrote alongside a photo gallery of her daughter, adding, "(Asking a mom to pick 10 photos of her first born is THE hardest thing I've ever had to do!)"
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Elton John and David Furnish's older son Zachary Jackson Levon rang in his 7th birthday on Christmas Day, with a special cake that may hint he will follow in John's musical footsteps.
"Happy Birthday Zachary!! Can't believe you are 7 today. You were the best Christmas present ever," the piano rocker captioned a heartwarming tribute post.
"What a difference you and your brother have made to our lives," added John (he and Furnish also share son Elijah Joseph Daniel, 5 next month). "We love you so much! Daddy and Papa xoxo."
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"Happy birthday Jameson Moon. Your family loves you to the sun and back," Pink captioned the post.
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FAITH KIDMAN URBAN
"HAPPY 7th BIRTHDAY FEEF - we LOOOVE you. Mum and Dad xxxxxx," Urban captioned an image of a large number 7, in front of the Sydney skyline.
Wrote Kidman alongside the same photo, "Happy Birthday to our baby girl who is now 7. You are so gentle and kind and loving and bring us joy joy joy darling girl. It is a blessing to be your parents.❤️❤️❤️"
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