Sylvester Stallone Posts Photo of Jennifer Flavin Amid Divorce Drama

Sylvester Stallone is raising some eyebrows with his latest post ... dropping old photos with his estranged wife Jennifer Flavin as they go through an ugly divorce.

Sly posted the pics Monday on IG -- the first one appears to be an old pic of Jennifer and him holding hands. In the second pic Sylvester, Jennifer and their 3 daughters are smiling and looking happy together as a family ... it's obvious it was taken many years ago.

He seemed to be taking a trip down memory lane ... adding a simple but vague caption, "Wonderful…"

It's interesting timing for sure ... you'll recall, Jennifer filed for divorce from Sly last month after 25 years of marriage, noting their union was "irretrievably broken."

She also accused the actor of moving assets from marital funds ...  and he's fired back, denying that.

As we've reported, Sly told us he and Jennifer had just grown apart -- though he acknowledged they also argued about his Rottweiler, Dwight -- making it clear the marriage was dunzo and saying they wanted to work deal with everything privately.