Bill Garrahan was the eldest son of Vivian Garrahan.
Unlike the rest of his family, Bill had a lesser view on the welfare of the company's miners and distastefully viewed strikers as communists. He had less faith in his mother's excavator power armor project and accurately called the "Man Versus Machine" challenge against Hornwright Industrial a major mistake. Bill also did not approve of his mother's marriage to Brighton Gould, whom he believed married for the family's fortunes rather than love.
Following an incident in which Bill scared off striking miners from his family's estate, he purchased a minigun which he named "Strike Beater" to use against the miners, would the need arise. When the miners began their revolt in early October 2077, Bill saw the opportunity to use his weapon against the miners at Mount Blair while also deliberately damaging the Hornwright-owned Rockhound excavator. Bill's actions, however, only further damaged the company's image and nearly ruined Bryce's peaceful negotiations with the miners.
Bill Garrahan is mentioned only in Fallout 76.