He captioned the post "wonderful", with one image showing the actor and Flavin smiling with their three daughters when they were grade school age, and a second showing Stallone and Flavin from behind, walking hand-in-hand in the sunny countryside.
When Flavin filed for divorce from Stallone on August 19 she said he had "engaged in the intentional dissipation, depletion and/or waste of marital assets, which has had an adverse economic impact on the marital estates" - an allegation denied by Stallone.
Days before the filing, the actor had a huge tattoo of Flavin on his right bicep covered up with a picture of Butkus, the bull mastiff from the Rocky films.
There were claims the couple's Rottweiler Dwight was the cause of the break-up. Stallone dotes on the dog, but insiders said Flavin objected to it being indoors.
The pair, who married in May 1995, share daughters Sophia, 26, Sistine, 24, and 20-year-old Scarle.
Stallone also has a son named Seargeoh, 43, with his ex, Sasha Czack, 72, who he married in 1974 and divorced nine years later.
He also had a son named Sage with Sasha, but he died in 2012 from heart disease, aged 36.
