The Starfleet officer and late husband of Lwaxana Troi, father of Deanna and Kestra.
Ian Andrew Troi was a human Starfleet officer who married Lwaxana Troi and fathered two daughters, Kestra and Deanna. He died when Deanna was a child, and his memory remains precious to both his wife and his surviving daughter.
In Dark Page, Deanna encounters an image of her father while exploring her mother's comatose mind. The vision guides her toward the memory of Kestra's death, which Lwaxana had hidden from everyone, including her younger daughter.