Aaron Jacobs was an ancestor of Alec Aaron Jacobs who died in 1840 when his mother, who was possessed by his aunt Ginerva Jacobs, murdered him. His ghost appeared to warn Egon and Janine that Ginerva would do the same to his descendant by possessing his mother Michele. When Egon and Janine went back in time and destroyed Ginerva before she could kill her nephew, history was altered so that Aaron lived a much longer life and died presumably of natural causes.