Kirby died Monday in Los Angeles from complications related to leukemia, his wife, Lynn Sellers, said in a statement Tuesday. He had been recently diagnosed with the disease.
"We are incredibly grateful for the outpouring of support we have received from Bruno's fans and colleagues who have admired and respected his work over the past 30 years," his wife said. "Bruno's spirit will continue to live on, not only in his rich body of film and television work but also through the lives of individuals he has touched throughout his life."
Born Bruno Giovanni Quidaciolu in 1949 in New York City, he was the son of actor Bruce Kirby. His early work included the 1971 film "Young Graduates," as well as appearances on the television show "Room 222" and the made-for-TV movie "The Summer Without Boys."
In 1974, he scored a role in "The Godfather: Part II," which won several Academy Awards, including best picture. In the film, Kirby played young "Pete Clemenza," following Richard S. Castellano's role in the first installment.
Over the next few years, Kirby made various TV appearances, including "Fame" and "Hill Street Blues," before landing the role of "2nd Lt. Steven Hauk" in Robin William's "Good Morning, Vietnam."
That was followed two years later by the romantic comedy "When Harry Met Sally," in which Kirby played Crystal's best friend. In 1991, Kirby once again appeared as Crystal's cheery friend in "City Slickers," along for a mid-life adventure driving cattle on a dude ranch.
He also appeared in 1997's "Donnie Brasco," and recently in an episode of the HBO hit series "Entourage."
Along with his wife and father, Kirby is survived by his stepmother Roz Kirby, brother John Kirby and stepbrother Brad Sullivan.
No information on funeral arrangements was immediately available.