Greg was born in San Diego, California, on August 20th, 1951, to Wilma M. and Dale F. Bear. His father was in the navy, and by the time he was twelve years old, he had traveled with his parents to Japan, the Philippines and Alaska, as well as touring various parts of the United States.
The first novel, Hegira (Dell), was sold in 1979. In 1983 Greg was nominated for the Nebula Award for my short story, "Petra." In 1984, "Hardfought" and "Blood Music" won the Nebula Awards for best novella and novelette, respectively; "Blood Music" went on to win the Hugo Award. The novel version of that story, also called Blood Music, won the Prix Apollo in France and was nominated for the Hugo and Nebula awards. In 1987, "Tangents" won the Hugo and Nebula awards for best short story. Moving Mars (1993) won the 1994 Nebula for best novel.
A short story, "Dead Run," was adapted by Alan Brennert for the second Twilight Zone television show. "The White Horse Child" appeared in 1993 as a CD-ROM multi-media presentation from EBOOK.
Occasional work as a freelance journalist has took Greg to the Jet Propulsion Laboratory in Pasadena, where he covered all the the Voyager planetary encounters for the San Diego Union. He has also written numerous articles on film for the Los Angeles Times. Between 1979 and 1982 he reviewed books for the San Diego Union Book Review supplement.
With his wife, Astrid, he co-edited the FORUM of the Science Fiction Writers of America for two years. For two years, he acted as chairman of the SFWA Grievance Committee, then served as Vice President of SFWA for a year, and President for two years (1988-1990). Between 1983 and 1990, he served on the Citizens Advisory Council on National Space Policy, a private group consisting of scientists, military specialists, space scientists and engineers, astronauts, and writers. He has consulted with Microsoft and other software companies, as well as WNET-13 New York, and served as science and speculations advisor for the pilot episode of the Amblin/Universal TV production "Earth 2."
In 1983, Greg married Astrid Anderson. His son Erik was born in September 1986. Their second child, Alexandra, was born in January of 1990.