Sylvester Stallone looks calm & cool at brother Frank's concert amid divorce

Hollywood actor Sylvester Stallone appeared composed and collected despite the Jennifer Flavin divorce.

The 76-year-old actor made a guest appearance at a concert that his brother, musician Frank Stallone, headlined at the Hard Rock Hotel and Casino in Atlantic City, New Jersey, on Friday evening.

The Rocky actor looked upbeat and enthusiastic onstage showing no signs of distraction despite the split as he was the first to greet the crowd at the show, telling audience members before him, "The bright lights of show biz. Thank you. Thank you. I appreciate it."

Sylvester's outing with his brother came about after Flavin, 54, filed for divorce from the star in a Palm Beach, Florida, courthouse on Aug. 19.

A Hollywood source, who has spent time with the couple, recently told PEOPLE that Stallone and Flavin "are very different people, age-wise and in temperament. What was once exciting and challenging is now routine and irritating."