'Godfather Part II' Star John Aprea Dead at 83

John Aprea , one of the stars of "The Godfather Part II" and "Full House," is dead of natural causes ... TMZ has learned.

His manager Will Levine tells us ... the actor passed away on August 7, at his home in Los Angeles, with family members by his side.

John called his role as young Salvatore Tessio his greatest career achievement. He had originally auditioned to be Michael Corleone in the OG 'Godfather,' which of course went to Al Pacino . But, Francis Ford Coppola called back Aprea for the 1974 sequel.

John's successful career actually started with another classic, as he made his acting debut in 1968 in Steve McQueen 's "Bullitt."

In the '80s and '90s he appeared on several TV shows, including "Knots Landing," "Falcon Crest," "The Gangster Chronicles" and "Full House" -- how's that for range?!

Aprea played Nick Katsopolis, the father of John Stamos ' Uncle Jesse character -- and he returned in that role for the reboot, "Fuller House."

He had a couple of stints in Daytime TV, too, appearing on "Another World" for several years in 2 different roles.

His friend and former "Knots Landing" costar Paul Carafotes posted a touching tribute to Aprea, saying "Many will miss this man."

John was 83.

RIP