Robert W. Foster died Tuesday in Columbus, Ohio. He was 78, the Columbus Dispatch reported Friday.
Foster, who was one of the Secret Service agents charged with protecting the children of President John F. Kennedy, also served as a U.S. marshal for southern Ohio and sergeant-at-arms for the Ohio General Assembly.
Foster guarded the Kennedy children from 1961 until 1964.
Foster's ex-wife, Peggy, recalled a comment by the president's father, Joseph Kennedy: "Mr. Foster, how does a Republican from Columbus, Ohio, wind up guarding my son -- a Democrat from Massachusetts?"
Andrew Foster said his father never let politics interfere with his professional duties.
"He took an enormous amount of pride in his affiliation to the Secret Service," Andrew Foster said.
After Jacqueline Kennedy and her children moved to New York in 1964, Foster took on other Secret Service assignments. He retired from the Secret Service in 1978, after serving as the special-agent-in-charge of the Columbus office.
He was a marshal from 1981 to 1994 and sergeant-at-arms through 2001.