Isaac Garrahan was the son of Vivian Garrahan and brother to Bryce and Bill. Unlike his family members, he had no interest in the family business or mining. Instead, he was obsessed with sloths, keeping a population in luxurious enclosures at the family's estate in Bramwell. However, his constant daydreaming led to lapses in security, where sloths would flee the enclosures and hide across the estate, such as in Bill's room. This did not endear the daydreamer to his family members, on the contrary.
Isaac Garrahan is only mentioned in Fallout 76.