Burt Young, a former boxer who found fame playing tough guys in Hollywood, died earlier this month, his daughter Anne Morea Steingieser told the New York Times.
He was 83.
CNN has reached out to Young's manager for comment.
Young was best known for his role as Rocky Balboa's brother-in-law Paulie in the "Rocky" movie franchise. He earned a best supporting actor Academy Award nomination for his performance.
Sylvester Stallone, who starred as Rocky, paid tribute to Young on Wednesday.
"To my Dear Friend, BURT YOUNG, you were an incredible man and artist, I and the World will miss you very much...RIP," Stallone wrote with a photo of him and Young in a scene from one of their films together.
Born in the New York City borough of Queens, Young grew up in the working class neighborhood of Corona before entering the Marines at the age of 16 after his father helped him lie about his age, according to the Times.
He began boxing in the Marines and continued once he left the service, briefly as a professional under the tutelage of famed trainer and manager Cus D'Amato.
Young explained in a 2006 interview with Bright Lights that he got into acting in his twenties because a young woman he was interested in "said she'd always wanted to study with Lee Strasberg, but couldn't get in."
"I didn't know who Lee Strasberg was. I thought it was a girl," Young recalled. "But I figured maybe if I could help her out, I could hold hands with her. But when I wrote to Strasberg, he took me seriously."
Acting, Young said," had everything I was fishing for."
"In my life till then, I'd used tension to hold myself upright," he said. "Lee's great gift to me was relaxation."
His first credited role was as a bartender in an episode of "The Doctors"in 1969, but his career as a character actor soon took off with roles in television series like "M*A*S*H" and "Little House on the Prairie," as well as films like "Chinatown" and "Serpico."
Young's role as Paulie in the hit 1976 film "Rocky" helped take his career to the next level. He told "The Sweet Science" in 2009 that he was the only actor who didn't have to audition.
"I was on the MGM lot when Sly Stallone came over and introduced himself to me, told me he wrote 'Rocky' and said 'you gotta do it,'" Young recalled. "I wanted to do it right away, but wanted to twist their arms a little bit, not look too eager."
"I thought the script had the cleanest street prose I'd ever read," he added. "Stallone is not only a workaholic, he's a genius who is always looking three years ahead. He has a real eyeball for what's going on in the world."
It helped establish Young as an actor who could play the heavy, but also be complex.
His career found him doing everything from appearing opposite Robert De Niro and Ralph Macchio in "Cuba and His Teddy Bear," which ran both off and on Broadway, to playing veteran mobster Bobby Bacala Sr. in "The Sopranos."
More recently, Young appeared in "Kevin Can Wait" and "Russian Doll." He was also attached to several projects in production at the time of his death, according to his IMDb profile.