Brother Adrian is an unseen character in Grand Theft Auto V.
He is mentioned several times by Audrey between songs on Self-Actualization FM in Episodes From Liberty City. However, he makes no appearance outside these messages. Cultstoppers notes that he owns the station.
He later makes an appearance in GTA V. At some point of the storyline, he will send various text messages to Franklin Clinton and will try to convince him to join by giving him their website address and a form to complete. Franklin can do this and will receive another text from him which will give Franklin a password to access the stage two part of the movement. After Franklin completes all the steps on the website, he will receive a Children of the Mountain t-shirt in his wardrobe and Brother Adrian will tell him that he will keep in touch with him.
He also appears as a guest on West Coast Talk Radio and speaks with an Irish accent. He is derided by Lazlow Jones many times during the show, who calls him a "wackjob", "cultist" and "pervert". He tries making it up to Lazlow, only to cause the latter to go through a mental breakdown on air.