The death was "sudden" and "a total shock," Gerald Casale said in a statement posted on Facebook.
The group was best known for the 1980 hit "Whip It." The band consisted of the Casale brothers, Mark and brother Bob Mothersbaugh and drummer Alan Myers.
"As an original member of Devo, Bob Casale was there in the trenches with me from the beginning," Gerald Casale said. "He was my level-headed brother, a solid performer and talented audio engineer, always giving more than he got."
The Ohio-based Devo introduced themselves to the world in 1977 by making a frenetic version of the Rolling Stones' "Satisfaction." The new wave band released its Brian Eno-produced debut, "Q: Are We Not Men? A: We Are Devo!," in 1978 and reached platinum status with 1980's "Freedom of Choice," which featured "Whip It."
Devo is short for devolution, the idea that man was regressing into an earlier state.
The Associated Press contributed to this report.