On Sunday, the Rocky actor shared family photos featuring himself, Sophia, and Jennifer Flavin in honor of his daughter's special day, which took place Saturday.
"A VERY HAPPY BELATED BIRTHDAY TO MY VERY SPECIAL DAUGHTER, SOPHIA!!" Stallone, 76, wrote in the Instagram caption alongside a carousel of family images. Flavin, 54, filed for divorce from Stallone on Aug. 19.
In one snap, Stallone and Sophia were seen flashing big grins posing next to a golf cart while the two enjoyed some father-daughter time.
Another photo shows a selfie of Stallone, Sophia, and Flavin as the group sits in what appears to be a vehicle. The trio was pictured in great spirits.
Another image in the post again features the trio dressed to the nines while striking a pose for the camera.
On Saturday, Flavin also honored her daughter's milestone by posting photos of Sophia and a throwback photo of the mother-daughter duo, but did not feature any images of Stallone.
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Sophia's celebratory posts from the former couple came after Flavin filed for divorce from Stallone last Friday.
She filed a petition "for dissolution of marriage and other relief" from the actor at a court in Palm Beach County, Florida.
The pair wed in 1997 after first meeting in 1988 at a restaurant in Beverly Hills, California. This past May, they celebrated 25 years of marriage as Stallone praised Flavin as an "incredibly selfless, dedicated, patient, woman." Flavin wrote in a now-deleted post, "Our marriage keeps getting better every year! I can't wait to spend the rest of our lives together!"
In addition to Sophia, the former couple share two other daughters, Scarlet, 20, and Sistine, 24. Stallone is also a father to son Seargeoh from his previous marriage to Sasha Czack. His oldest son Sage, whom he also shared with Czack, died in 2012.
In an exclusive statement to PEOPLE last week, Flavin said she'll "always cherish" her relationship with Stallone.
"I'm sad to announce that after 25 years of marriage, I have filed for divorce from my husband, Sylvester Stallone. While we will no longer be married, I will always cherish the more than 30-year relationship that we shared, and I know we are both committed to our beautiful daughters," she said.
"I ask for privacy for our family as we amicably move forward," the model added.
Stallone also told PEOPLE, "I love my family. We are amicably and privately addressing these personal issues."