Not much is known about Hobbes' past, other than that he was the brother John Hobbes and married at some point, having a son, Sam, thereafter, and apparently having his wife leave him or die on him. He and Sam afterwards moved in with his brother in his apartment. He was apparently born with a kind of mental handicap, causing him to be forever a child in his mind, even as a man.
Art Hobbes made his debut in the film at the apartment he and his son, Sam, shared with hid brother, Detective John Hobbes, making Sam's lunch before he left for school, and conversing with his brother about whether he and Sam living there was a burden, and that maybe his wife Marcie might not have left if it hadn't been for that. John, however, denied both these things, saying family is always first. He is later seen be woken up by John after falling asleep with Sam watching something, and answered the phone when it rang, with nobody on the other side. After it rang again, he asked John if he ever got scared, before going to bed. Hobbes is not seen again until his brother came home from work early one day, and asked him whether he had moved his address book, before following up with who had blacked his right eye. He answered that Sam had, but that it was an accident. Later that night, Hobbes and Sam appeared at the scene of a crime his brother was working, but he ordered them to go home and lock ever door and window in the apartment and let nobody inside. Before they left, Hobbes asked John if he was mad at him, but the latter denied that, and they went home. Though Hobbes was still alive when his brother finally got back later, at some point following this he was possessed by the demon Azazel, who had possessed Sam when he hit him, and forced to write the letter "y" on his son's chest, before afterwards being forced to commit suicide with a syringe of poison.
because of his handicap, Art Hobbes was a very childish man mentally, but was nonetheless able to understand the true meaning of love, adn showed throughout the film to be a loving brother and father. He had a close relationship with his brother, John, and his son, Sam, with John openly admitting that him and Sam living in his apartment was no burden, and crying for Hobbes after he was murdered by the demon Azazel.