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A sister ship was a ship of the same class as, or virtually identical to, another ship. The term was used by the Federation, Klingons, and Romulans.
Launched in 2154, Columbia was the sister ship to Enterprise. Both were NX-class vessels, though Columbia sported many new and redesigned systems. (ENT: "The Expanse", "E²", "Home", "Affliction")
By 2256, the two Crossfield-class starships USS Discovery and USS Glenn were considered sister ships. (DIS: "Context Is for Kings")
The Federation Constitution-class heavy cruisers USS Enterprise and USS Constellation were sister ships during the 23rd century. (TOS: "The Doomsday Machine")
Similarly, the USS Enterprise-D and USS Yamato were also referred to as sister ships. Both were Galaxy-class starships. (TNG: "Where Silence Has Lease", "Contagion")
The IKS Klothos and Kuri's battle cruiser were sister ships. Following his witnessing of the Klothos's destruction, Kuri blamed the Enterprise and ordered them to surrender. (TAS: "The Time Trap")
The entity known as Tin Man destroyed the sister ship of a Romulan warbird in 2366, prompting a claim of Right of Vengeance from the warbird's commander. (TNG: "Tin Man")