Born in Portland, Maine, to Greek immigrants,[1] Kyros attended the Portland Public Schools completed an engineering program at the Massachusetts Institute of Technology.

Kyros served in the United States Navy from 1944 to 1953 and was discharged with rank of lieutenant.

He was admitted to the bar in 1957 and commenced the practice of law in Portland, Maine.

From 1957 to 1959, Kyros served as counsel to the Maine Public Utilities Commission.

Kyros resumed the practice of law in Washington, D.C., lobbying "for several firms active on Capitol Hill, advocating for scientific and medical research".