FLASHBACK: Sage Stallone and Father Sylvester in 'Rocky V'

They were father and son in the movies, too.

Sage Moonblood Stallone, who was found dead Friday at age 36, acted with his father Sylvester in one of the elder Stallone’s biggest franchises – the Rocky series – playing Rocky Balboa Jr. in Rocky V.

Sage, who was 14 when the movie was released in 1990, was “agreeably natural in some scenes, improbable in others,” New York Times critic Janet Maslin wrote in her review at the time.

In any case, it was Sage’s first on-screen taste of Hollywood. And while he would not become a major star in his own right, he would work in films for the next two decades. He appeared with his father again in 1996’s Daylight and wrote and directed the 2006 short Vic.

There were no signs of foul play or forced entry when police were called to Sage’s Hollywood home at 2:17 p.m. Friday and discovered his body, initially found by a housekeeper.

Some published reports have suggested he may have overdosed on prescription drugs, but that speculation remains unconfirmed. An official cause of death will take weeks for the coroner to determine.

A rep for Sylvester Stallone, 66, said the Hollywood legend is “devastated and grief-stricken,” adding that Sage – whose mother was Sylvester’s first wife, Sasha Czack – was “a very talented and wonderful young man.”

Sage’s attorney, George Braunstein, told PEOPLE on Friday that there was “no indication there was any problem” with Sage, and that he seemed happy and was even planning to get married.