On 9th of April 1984, John got married to one of the most reputed American actress Gena Rowlands. Gena Rowlands is also a film director and she has been active in the film industry since the 1950s. As a husband and wife, they had three children together.
After spending several years in Greece, John moved to United Stated at the age of 7. During that time, he was not able to speak English. He was raised in Long Island, New York and there he attended Port Washington High School. He studied there for about two years and then he joined Blair Academy and Champlain College. He also got enrolled at American Academy of Dramatic Arts, and he graduated from there in 1950. He made his acting debut in 1950s by starring in the film Noir drama film Fourteen Hours. Two years later, he starred in the movies like Taxi and You Are There. He got his rise in fame in 1967 after she was seen playing the role of Victor Franko in an American war film The Dirty Dozen. He also got his first nomination in the awards like Academy Awards, USA and Golden Globes, USA from this role. At the age of 59, his health gets a serious turn as he was diagnosed of cirrhosis of the liver and he died of this disease on 3rd of February 1989. At the time of his death, his net worth was $40 million dollars.