Sylvester Stallone is known for starring in the iconic film series Rocky. The now 74-year-old actor wrote the script for the 1976 film in only 3 days. He was inspired by a boxing match between Muhammad Ali and Chuck Wepner. The film was also shot in just 28 days with a small $900,000 budget. Despite working on the film under stressful conditions, it instantly brought Stallone into stardom. The film series led him to more projects that made him the legendary action movie star that he is now.

But what most people don't know is that the Demolition Man wasn't the only Stallone working behind the scenes of these Rocky films. There's a lesser-known Stallone brother who's quite an achiever in his field, too. His name is Frank Stallone Jr., Sly's only full biological sibling. He wrote the catchy song Take You Back for Rocky III. Here's everything else you should know about the Academy Award nominee's younger brother.

Frank Stallone Jr. was born on July 30, 1950. He is the youngest son of astrologer and psychic Jacqueline Stallone and Italian-American hairdresser Frank Stallone Sr. Sly and Frank Jr. have three half-siblings on their father's side: Bryan, Carla, and Dante who's 50 years younger than the Rambo star. They also had a half-sister on their mother's side named Toni D'Alto. She played a role in the 1996 film The Appointment and died of lung cancer in 2012.

In September 2020, Frank Jr. was the one to announce their mother's passing. Jackie died at the age of 98. Sly's younger brother wrote in an Instagram post, "She died in her sleep as she had wished. It was hard not to like her, she was [a] very eccentric and flamboyant person." The cause of Jackie's death wasn't revealed in the post. "She lived through prohibition, the depression, and World War II. I would talk to her for hours about the 20s, 30s, and 40s. It was a history lesson. Her mind was as sharp as a razor till the day she died. She never wore a mask a true revolutionary gal," Frank Jr. added.

Jackie Stallone's career as an astrologer earned her a number of TV appearances in the 90s.  She even had her own psychic hotline. She also originally coined the term and practice of rumpology which is reading other parts of someone's body like a psychic would read one's palm. She was truly a star in her own right, joining at least two seasons of Celebrity Big Brother in the UK. Saturday Night Live had even parodied her unique character before. Entertaining indeed runs in the family, but wait until you learn about Frank Jr's career.

What Does Frank Stallone Jr. Do?

Frank is a well-known guitarist, actor, and musician. He has composed music for many of his brother's films like Rocky. He also wrote Far from Over which was featured in the 1983 film Staying Alive. It was a global hit that remained at the top of musical charts for months. The younger Stallone even earned a Grammy nomination for Best Original Song and a Golden Globe nomination for Best Soundtrack. He's definitely conquered music on his own, veering away from the shadow of the Expendables star.

The 70-year-old musical artist has done countless shows in his theaters and concert halls throughout his lifetime. This got him recognition from music icons like Frank Sinatra, Sammy Cahn, and Tony Bennett. Although his brother Sly took over the acting field, Frank still made pretty memorable appearances in films like Paradise Alley, Prime Suspect, Midnight Cop, and Order of the Eagle. He even appeared in the 2006 Rocky Balboa.

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What's The Stallone Brothers' Relationship Like?

Aside from music, Frank shares Sly's love for combat sports. He's also a boxing enthusiast. He even made guest appearances in boxing shows. He had a boxing match with TV reporter Geraldo Rivera which he won and had also joined Hulk Hogan's Celebrity Championship Wrestling. No wonder he's close with the Creed star. But perhaps their ultimate bonding is when they work together on Sly's film projects.

Frank said the only reason he's written for his brother's music is: "I was the only musician my brother, Sylvester, knew…and I worked cheap." But surely, with his prestigious award nominations, he's already earned his own stripes. He also said in interviews that he doesn't feel overshadowed by his movie star brother at all. Frank and Sly are also big family guys. Frank may have "forgot" to get married, but the musician loves spending quality time with his brother's family a lot. They celebrate birthdays and special occasions together.

NEXT: Everything We Know About Angelina Jolie's Relationship With Her Brother, James Haven