Billy was born in Clay Center, Kansas, the only child of N.L. Hillman and Velma Rose Woods. After two years in the Army he obtained a BA from Whitworth College and then got his MA in teaching from Reed in 1963. He received his master’s of education and a PhD in educational psychology from the University of Oregon. For 28 years he was a professor of counseling and guidance at the University of Arizona.
After retiring, he established a private practice for 10 years as a family and relationship therapist. He served as president of the Arizona chapter of the American Association for Marriage and Family Therapy and was an active member of the Immanuel Presbyterian Church. A respected author and teacher, he extended his knowledge and caring spirit to numerous humanitarian causes and interfaith organizations, such as the Southern Arizona LGBT Faith Alliance and Humane Borders.
He enjoyed reading, hiking, fishing, camping ,and travel abroad. Billy is survived by his wife of 58 years, Betty Marie (Bartke) Hillman, whom he met in the sixth grade in Concord, California; two daughters, Debi Demijohn and husband Russell, and Susan de Alban and husband Luis; and two granddaughters, Laurissa and Kimberly Demijohn. His eldest daughter, Cindy, preceded him in death.