He was born in Cleveland, Ohio, the older of two sons, along with brother Charles, born to Raymond B. and Lola G. Forssi. When he was about 9 years old, his family moved to Siesta Key, on the Florida west coast, and shortly thereafter to the nearby city of Sarasota. Ken Forssi attended Sarasota High School where he demonstrated considerable talent in engineering drawing. Several pen and ink drawings, of the multi-geared transmission of a helicopter and of a large jet aircraft engine, won local prizes, and he was encouraged to follow a career in that field. He also proved to be mechanically skilled as a teenager, working on both motorcycles and cars, sometimes as a paid part-time employee of local businesses. He was eventually employed as a draftsman at a large Sarasota aerospace engineering company.