He and wife Sandra Evelyn Winters had two children, April Rose (B. August 9, 1954-D. March 21, 2011) and Walden William. After August Derleth's death in 1971, both April and Walden became owners of Arkham House Publishers, which had been founded by their father in 1939 with author Donald Wandrei for the sole purpose of publishing H.P. Lovecraft. In 1994, April became majority stockholder, President and CEO of Arkham House and remained in that capacity until her passing at her home in Sauk City, Wisconsin of natural causes.
Literary executor of H.P. Lovecraft. He was also responsible for finishing certain incomplete Lovecraft stories and seeing them published.