He was the father of Derrick, Gerald, Patrick, Francis, and Kate McReary, and husband of Maureen McReary. He committed suicide in 2000. Packie mentions that he used to abuse his boys, but left Kate alone. Maureen states that he is most likely in Hell. In one mission, there is a portrait above Maureen McReary's fireplace that shows what Mr. McReary looked like.
When Patrick and Niko hang out, Patrick may open up to Niko, and tell him that he was almost molested by his father, but Gerry stopped him and beat their father to a pulp. He calls his father a "pervert" and condemns his memory to "the seventh circle of Hell". Maureen is extremely upset over his death.
There is a portrait in Oleg Minkov's apartment above his fireplace of Mr. McReary and Maureen McReary as seen in the mission Wrong is Right. This is because in the files, the model fireplace is attached to the picture frame, so when used in Oleg's apartment, the picture went with it.
It can be assumed that Mr. McReary was arrested for Murder in or before 1950 and became a fugitive in or before 1961 since his wife Maureen has convictions for Accessory to Murder and Harboring a Fugitive in those years and is stated in the LCPD database to have been a conspirator with him in the 50's and 60's.