Lieutenant Ian Andrew Troi was a Human Starfleet officer and husband of Betazoid Ambassador Lwaxana Troi. Ian and Lwaxana married in 2328, and had two daughters, Kestra and Deanna. However, Kestra drowned shortly after Deanna was born and, at the request of his grieving wife, Ian never mentioned his first-born daughter again. Ian worshiped Lwaxana, despite her unique perspectives on Human men. (TNG: "Manhunt", "Dark Page")
Ian apparently acceded to most of the cultural expectations of his strong-willed wife, living on Betazed and arranging for his daughter, Deanna, to be genetically bonded to Wyatt Miller, the son of his friends, Steven and Victoria Miller, in accordance with Betazoid tradition. One aspect of Human culture which Ian Troi passed on to his daughter was a fondness for stories of the American "Ancient West". (TNG: "Haven", "A Fistful of Datas") He would also often sing her to sleep, particularly with the song "Down in the Valley". (TNG: "The Host", "Dark Page")
Ian Troi was seen in flashback in the episode "Dark Page", and was played by actor Amick Byram. The circumstances of Ian's death were never revealed. According to his daughter's personnel file, shown in TNG: "Conundrum", he also went by the name "Alex Troi".
His rank is derived from his Star Trek films-era Starfleet uniform (modified without the turtleneck, as seen in "Tapestry" and "Yesterday's Enterprise"). The color of his collar and the small turtleneck suggests he was an engineer. He appeared as a figment of a hallucination, in the crew quarters set with a daytime window background.
The novel The Art of the Impossible establishes that Troi died when a building he and Elias Vaughn were investigating collapsed on top of them due to Romulan sabotage. As a close friend of Troi, it was Vaughn who told Lwaxana and Deanna of Troi's death and brought his body to them on Betazed. Troi was a lieutenant commander on the USS Carthage, on which he served as science officer with future Captain Rachel Garrett.