D'Tan believed that Romulus would someday reunify with Vulcan. He was influenced by his parents, who taught him the Vulcan language. One of his favorite books was one that told the story of the Vulcan separation. D'Tan participated in underground efforts to bring Romulan society closer to this reunification. He was a friend of Ambassador Spock and a member of Spock's underground movement for Vulcan-Romulan reunification. (TNG: "Unification II")
D'Tan has been mentioned in virtually every book featuring Spock on Romulus, and appears in the Star Trek: Titan novel Taking Wing, where he met Tuvok in the sewers of Romulus where the unification movement maintained a base. D'Tan also appears in the Star Trek: Typhon Pact novels Rough Beasts of Empire and Plagues of Night.
D'Tan is also featured in Star Trek Online. D'Tan and his followers survived the destruction of Romulus in 2387, and joined the Reman resistance under Obisek to establish Mol'Rihan (New Romulus) as the capital world of the Romulan Republic, a peaceful, open state, in opposition to the society of fear and deception within the Romulan Star Empire, as led by Empress Sela and the Tal Shiar. D'Tan is named Proconsul by popular acclamation, and leads the Republic as part of the leading trifecta of the "Alliance", alongside the Federation and the Klingon Empire.