He passed away in Rochester, New York on Thursday (27May10) at the age of 57.
Keefe enjoyed a career in animation spanning more than two decades, creating and producing hours upon hours of kids and family shows.
He began adapting Japanese cartoons like Go Lion and Dierugger for western audiences in the mid-1980s and created his most famous franchise, Voltron.
The animated series began syndication in the U.S. in September, 1984 and still continues to draw viewers across the world in more than 100 countries.
It also served as the inspiration for other hugely popular cartoons Pokemon and Power Rangers, according to the Hollywood Reporter.
Keefe's other creations include Denver, the Last Dinosaur, Widget, The Mr. Bogus Show and Twinkle.
He is survived by his wife Pamela Mills Keefe, stepson James, mother Anne, three sisters and two brothers.