Bear was born in San Diego, California. From 1968 to 1973 he attended San Diego State University, where he received a Bachelor of Arts degree. In 1975, he married Christina M. Nielson, but they divorced in 1981. He remarried in 1983, to Astrid Anderson, the daughter of science fiction author Poul Anderson. They have two children, Erik and Alexandra. They live outside of Seattle, Washington.